#include <cstdio>
#include <cstring>

int n[25], k[2];
char ch[50];

int main(){
    scanf("%s",ch);
    int x = strlen(ch);
    for ( int i = 0; i < x; i++ )
        n[ch[i]-'a']++;
    for ( int i = 0; i < 24; i++ )
        if ( n[i] > k[0] ){
            k[0] = n[i];
            k[1] = i;
        }
    printf("%c", k[1]+'a');
    scanf("\n");
    return 0;
}

Edited by author 25.08.2011 18:32

There are 26 letters in English alphabet =)
Also beware about /0 char in the end of line, use char ch[51], MAXLEN+1.

i change it and still wrong