[SOLVED]Why this c++ code isn't working properly for n>13?

Question

This program works fine for n<13. It does wrong division for p. (Eg for n=13 and r=4)

https://code.sololearn.com/cPw82NKfkJwn/?ref=app

#include <iostream>
using namespace std;

int factorial(int a)
{ long long int s=1;
for(int q=1;q<=a;q++)
{ s=s*q;}
cout<<s<<endl;
return s;
}

int main() {
long long int n,r;
long long int p,q,s;

cin>>n>>r;
q=factorial(n),s=factorial(n-r); p=q/s;
cout<<p;

return 0;
}

But if you try to do the division manually then it gives correct output.

https://code.sololearn.com/cILguJHQc37d/?ref=app

#include <iostream>

using namespace std;

int main()
{long long int i=6227020800; //13!
long long int j=362880; //13-4 ie 9!
long long int k=i/j;
cout<<k;
return 0;
}

Answer 1

Oh I got it,
I've to use

long int factorial (int a)

Instead of

int factorial (int a)