I am trying to write a program that determines if the sequence of characters is valid or invalid : <p>If the user enters any character other than ACGT (sequence does not matter) then it should print "INVALID". The user just keeps entering the sequence not more than 250 characters. </p>

<pre><code>#include &lt;stdio.h&gt;
#include &lt;string.h&gt;
int main(void)
{
    char dna[250];
int i;
for(i=0; i&lt;250; i++)
{
    scanf("%c", dna[i]);
}
fgets(*dna, 250, scanf("%c", dna));
int k;
for(k=0; k&lt;250; k++)
{
    if(dna[k] == 'A' || 'C' || 'G'|| 'T')
    {
        i++;
        //printf("%c\n", dna[0])
    }
}
if(i &gt; 0)
{
    printf("VALID sequence \n");
}
else
{
    printf("INVALID sequence \n");
}

}
</code></pre>
