#include <stdio.h>

int main(void) {
    const char *p1, *p2, *s1 = "foobar", *s2 = "foobaz";
    for (p1 = s1, p2 = s2 ; *p1 && *p1 == *p2 ; p1++, p2++);
    const char *p = *p1 || *p2 ? p1 : NULL;
    if (!p)
        puts("the strings are equal");
    else
        printf("s1 has %c, where s2 has %c\n", *p, s2[p - s1]);
	return 0;
}