my C program doesnt work the way its supposed to : I made this program but it doesnt work.

You enter two numbers.
Then you press + or -.
If you press + it should add the numbers.
If you press - it should  subtract.
But that part doesnt work.
```
#include <stdio.h>
#include <stdlib.h>

/* run this program using the console pauser or add your own getch, system("pause") or input loop */

int main(int argc, char *argv[]) {
char opt;       
int a,b,s;      
scanf("%d",&a);
scanf("%c\n",&opt);  
scanf("%d",&b);	
if(opt=='+') {	         //this part doesnt work
s=a+b;
}
else if(opt=='-') {
s=a-b;
}
printf("%d",s);
 return 0;
}
```
What should i do?