#include <stdio.h>
long long factorial(int n) {
    if (n == 0) {
        return 1;
    } else {
       return n * factorial(n - 1)
    }
}
int main() {
    int n;
    scanf("%d", &n);
    if (n < 0) {
        printf("Invalid Input\n");
    } else {
        printf("%11d\n", factorial(n));
    }
    return 0;
}