#include <bits/stdc++.h>
using namespace std;
int fac(int& ans,int& i,int n){
if(i==n){
return ans*n;
}
ans=ans*i;
i++;
return fac(ans,i,n);
}
int main() {
int ans=1;int i=1;int n=4;
cout<<fac(ans,i,n);
}
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