#include <iostream>
#include<ctime>
using namespace std;

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

int main()
{
    time_t s,e,sumtime;
    int n;
    cin>>n;
    s=clock();
    cout<<"fac("<<n<<")="<<fac(n)<<endl;
    e=clock();
    sumtime=e-s;
    cout<<"time:"<<sumtime<<endl;
    return 0;
}