#include <stdio.h>

int main()
{
    int n;
    long long factorial = 1;
    
    scanf("%d", &n);
    
    if (n < 0)
    {
        printf("Invalid Input");
        return 0;
    }
    for 9int i = 1; i <=n; i++)
    {
        factorial *= i;
    }
    
    printf("%lld", factorial);
    
    return 0;
}