#include <omp.h>
#include <stdio.h>

int main() {
    long long int total = 1, i;
#pragma omp parallel for reduction(*:total)
    for(i = 1; i <= 20; i++) {
        // printf("working in thread %d\n", omp_get_thread_num());
        total = total * i;
    }
    printf("total: %lld\n", total);
}