Derangement Number By Recursion

#include<bits/stdc++.h>

using namespace std;

int counter(int n)

{

    if(n == 0)

        return 1;

    else if(n == 1)

        return 0;

    else if(n == 2)

        return 1;

    return (n-1)*(counter(n-1) + counter(n-2));

}

int main()

{

    int n;

    cout << "Enter A Number :: ";

    cin >> n;

    int Derangement_Number = counter(n);

    cout << "\n" << n << " Element Derangement Number is :: " << Derangement_Number << "\n";

    return 0;

}