#include<stdio.h>

long long fac(int n)
{
    if(n==0)
    {
        return 1;
    }
    long long int fn = n* fac(n-1);
    return fn;
}


int main()
{

    int n =1;
    long long int fn;
    fn = fac(n);
    printf("%lld\n",fn);
}