#include <stdio.h>
#include <stdlib.h>

extern unsigned long long fib_iter(unsigned long long n);

int main(int argc, char *argv[]) {
    unsigned long long n, r;
    n = atoll(argv[1]);
    r = fib_iter(n);
    printf("fib(%llu) = %llu\n", n, r);

    return 0;
}