/*#include<bits/stdc++.h>
using namespace std;
iterative solution:
int fact (int n, int k)
{
if(n==0) return 1;
return fact(n-1,k*n);
}
int main()
{
int n,k=1;
cin>>n;
int ans=fact(n,k);
cout<<ans<<endl;
}*/
//recursive solution.
#include<bits/stdc++.h>
using namespace std;
int fact(int n)
{
if(n==0)return 1;
return n*fact(n-1);
}
int main(){
int n;
cin>>n;
cout<<fact(n)<<endl;
}