#include<stdio.h>
int main() {
    int n;
    long long factoorial = 1;
    scanf("%d", &n);
    if (n < 0) {
        printf("Invalid input\n");
    } else {
        for (int i = 1; i <= n; i++) {
            factorial *= i;
        }
        printf("%lld\n", factorial);
    }
    return 0;
}