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