Ex 3

#include <iostream>
using namespace std;
int factorial (int s, int d)
{
    if (s==d)
        return s;
    else {
        int m=(s+d)/2;
        return factorial(s, m)*factorial(m+1, d);
    }
}
int e (int s, int d)
{
    if (s==d)
        return factorial(1, s);
    else {
        int m=(s+d)/2;
        return e(s, m)+e(m+1, d);
    }
}
int main()
{
    int n;
    cin>>n;
    cout<<e(1, n);
    return 0;
}