// editor3
#include <stdio.h>
int main()
{
    int n,
    long,long fact = 1;
    scanf("%d", &n);
    if (n < 0)
    {
        printf("Invalid input");
        return 0;
    }
    for (int i =1;i <= n; i++)
    {
        fact *=i;
    }
    printf("%lld",fact);
    return 0;
}