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

int fact(int n, int factsofar) {
        if (n == 0) return factsofar;
        return fact(n - 1, n * factsofar);
}
int main(int argc, char *argv[]) {
        int x = atoi(argv[1]);
        printf("%d\n", fact(x, 1));
}