#include<stdio.h>
int main() {
    int n;
    scanf("%d", &n);
    if(n < 0) {
        printf("Invalid input\n");
        return 0;
    }
    long long fact = 1;
    for ( int i = 1; i <= n; i++) {
        fact *=i;
    }
    printf("%I1d\n", fact);
    retur
}