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