#include <stdio.h>

r;f(n){for(r=0;n/=5;)r+=n;return r;}

int main (int argc, char **argv) {
    int i;
    int testcases[] = {1, 5, 100, 666, 2016};

    for (i = 0; i < (sizeof(testcases) / sizeof(testcases[0])); i++) {
        printf("f(%d)=%d\n", testcases[i], f(testcases[i]));
    }

    return 0;
}