#include <assert.h>
#include <stdlib.h>

int prefix(char * pre, char * str) {
  if (!pre || !str) return 0;
  while (*pre)
    if (*pre++ != *str++)
      return 0;
  return 1;
}

int main() {
  assert (prefix("Milk", "Milkyway"));
  assert (!prefix("milk", "Milkyway"));
  assert (!prefix("ilk", "Milkyway"));
  assert (!prefix(NULL, "Milkyway"));
  assert (!prefix("Milkyway", NULL));
  return 0;
}