For this Question: Sansa has discovered Theon is at Winterfell. Ramsay is forcing him to apologize to her for supposedly killing her younger brothers. But Sansa will accept the apology string S if it satisfies the following conditions for a given value of N:
<li> String S should have exactly <b>N distinct substrings</b>.
<li> Length of the string should be minimum possible.
<li> Among all shortest strings, S should be lexicographically smallest one.The first and the only line of input contains an integer N.

Constraints
1 <= N <= 300Output the apology string S.Sample Input
3

Sample Output
ab

Explanation: Distinct substrings of ab are: "a", "b", "ab"

Sample Input
7

Sample Output
aaab

Explanation: Distinct substrings of aaab are: "a", "b", "aa", "ab", "aaa", "aab", "aaab", I have written this Solution Code: import java.util.*;
import java.io.*;
import java.math.*;




public class Main {

	public static void process() throws IOException {

		int n = sc.nextInt();
		int len = 1;
        while ((len*(len+1))/2 < n)len++;

        StringBuilder ans = new StringBuilder("");
        for(int i = 0; i< len; i++){
            for(char ch = 'a'; ch <= 'z'; ch++){
                StringBuilder tmp = new StringBuilder(ans);
                tmp.append(ch);

                char cc = 'z';
                for(int j = i+1; j< len; j++){
                    tmp.append(cc--);
                }
                if(count(tmp.toString()) >= n){
                    ans.append(ch);
                    break;
                }
            }

        }
        System.out.println(ans.toString());

	}
    static int count(String S){
        TreeSet<String> set = new TreeSet<>();
        for(int i = 0; i< S.length(); i++)
            for(int j = i; j< S.length(); j++)
                set.add(S.substring(i, j+1));
     	return set.size();
    }




	private static long INF = 2000000000000000000L, M = 1000000007, MM = 998244353;


	private static void google(int tt) {
		System.out.print("Case #" + (tt) + ": ");
	}

	static FastScanner sc;
	static PrintWriter out;

	public static void main(String[] args) throws IOException {
		boolean oj = true;
		if (oj) {
			sc = new FastScanner();
			out = new PrintWriter(System.out);
		} else {
			sc = new FastScanner(100);
			out = new PrintWriter("output.txt");
		}
		int t = 1;

		int TTT = 1;
		while (t-- > 0) {

			process();
		}
		out.flush();
		out.close();
	}

	static class Pair implements Comparable<Pair> {
		int x, y;

		Pair(int x, int y) {
			this.x = x;
			this.y = y;
		}

		@Override
		public int compareTo(Pair o) {
			return Integer.compare(this.x, o.x);
		}















	}



	static void debug(Object o) {
		System.out.println(o);
	}

	static void debug(Object x, Object y) {
		System.out.println("(" + x + " , " + y + ")");
	}

	static void println(Object o) {
		out.println(o);
	}

	static void println(int[] o) {
		for (int e : o)
			print(e + " ");
		println();
	}

	static void println(long[] o) {
		for (long e : o)
			print(e + " ");
		println();
	}

	static void println() {
		out.println();
	}

	static void print(Object o) {
		out.print(o);
	}

	static void pflush(Object o) {
		out.println(o);
		out.flush();
	}

	static int ceil(int x, int y) {
		return (x % y == 0 ? x / y : (x / y + 1));
	}

	static long ceil(long x, long y) {
		return (x % y == 0 ? x / y : (x / y + 1));
	}

	static int max(int x, int y) {
		return Math.max(x, y);
	}

	static int min(int x, int y) {
		return Math.min(x, y);
	}

	static int abs(int x) {
		return Math.abs(x);
	}

	static long abs(long x) {
		return Math.abs(x);
	}

	static long sqrt(long z) {
		long sqz = (long) Math.sqrt(z);
		while (sqz * 1L * sqz < z) {
			sqz++;
		}
		while (sqz * 1L * sqz > z) {
			sqz--;
		}
		return sqz;
	}

	static int log2(int N) {
		int result = (int) (Math.log(N) / Math.log(2));
		return result;
	}

	static long max(long x, long y) {
		return Math.max(x, y);
	}

	static long min(long x, long y) {
		return Math.min(x, y);
	}

	public static int gcd(int a, int b) {
		BigInteger b1 = BigInteger.valueOf(a);
		BigInteger b2 = BigInteger.valueOf(b);
		BigInteger gcd = b1.gcd(b2);
		return gcd.intValue();
	}

	public static long gcd(long a, long b) {
		BigInteger b1 = BigInteger.valueOf(a);
		BigInteger b2 = BigInteger.valueOf(b);
		BigInteger gcd = b1.gcd(b2);
		return gcd.longValue();
	}

	public static long lcm(long a, long b) {
		return (a * b) / gcd(a, b);
	}

	public static int lcm(int a, int b) {
		return (a * b) / gcd(a, b);
	}

	public static int lower_bound(int[] arr, int x) {
		int low = 0, high = arr.length, mid = -1;

		while (low < high) {
			mid = (low + high) / 2;

			if (arr[mid] >= x)
				high = mid;
			else
				low = mid + 1;
		}

		return low;
	}

	public static int upper_bound(int[] arr, int x) {
		int low = 0, high = arr.length, mid = -1;

		while (low < high) {
			mid = (low + high) / 2;

			if (arr[mid] > x)
				high = mid;
			else
				low = mid + 1;
		}

		return low;
	}



	static class FastScanner {
		BufferedReader br;
		StringTokenizer st;

		FastScanner() throws FileNotFoundException {
			br = new BufferedReader(new InputStreamReader(System.in));
		}

		FastScanner(int a) throws FileNotFoundException {
			br = new BufferedReader(new FileReader("input.txt"));
		}

		String next() throws IOException {
			while (st == null || !st.hasMoreElements()) {
				try {
					st = new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
			return st.nextToken();
		}

		int nextInt() throws IOException {
			return Integer.parseInt(next());
		}

		long nextLong() throws IOException {
			return Long.parseLong(next());
		}

		double nextDouble() throws IOException {
			return Double.parseDouble(next());
		}

		String nextLine() throws IOException {
			String str = "";
			try {
				str = br.readLine();
			} catch (IOException e) {
				e.printStackTrace();
			}
			return str;
		}

		int[] readArray(int n) throws IOException {
			int[] A = new int[n];
			for (int i = 0; i != n; i++) {
				A[i] = sc.nextInt();
			}
			return A;
		}

		long[] readArrayLong(int n) throws IOException {
			long[] A = new long[n];
			for (int i = 0; i != n; i++) {
				A[i] = sc.nextLong();
			}
			return A;
		}
	}

	static void ruffleSort(int[] a) {
		Random get = new Random();
		for (int i = 0; i < a.length; i++) {
			int r = get.nextInt(a.length);
			int temp = a[i];
			a[i] = a[r];
			a[r] = temp;
		}
		Arrays.sort(a);
	}

	static void ruffleSort(long[] a) {
		Random get = new Random();
		for (int i = 0; i < a.length; i++) {
			int r = get.nextInt(a.length);
			long temp = a[i];
			a[i] = a[r];
			a[r] = temp;
		}
		Arrays.sort(a);
	}

	static void reverseArray(int[] a) {
		int n = a.length;
		int arr[] = new int[n];
		for (int i = 0; i < n; i++)
			arr[i] = a[n - i - 1];
		for (int i = 0; i < n; i++)
			a[i] = arr[i];
	}

	static void reverseArray(long[] a) {
		int n = a.length;
		long arr[] = new long[n];
		for (int i = 0; i < n; i++)
			arr[i] = a[n - i - 1];
		for (int i = 0; i < n; i++)
			a[i] = arr[i];
	}

}, In this Programming Language: Java, Now tell me if this Code is compilable or not?