file.cpp

#include<iostream>
using namespace std;

int foo1(int n)
{
    if (n == 0)
    {
        return 3;
    }
    if (n == 1)
    {
        return 2;
    }
    else
    {
        return foo1(n-1) * foo1(n-2) - n;
    }
}

int foo2(int n)
{
    int nMinus2 = 3, nMinus1 = 2, result = 0;
    if (n == 0)
    {
        result = nMinus2;
    }
    else if (n == 1)
    {
        result = nMinus1;
    }
    else
    {
        for (int i = 2; i <= n; i++)
        {
            result = nMinus2 * nMinus1 - i;
            nMinus2 = nMinus1;
            nMinus1 = result;
        }
    }
    return result;
}

int main()
{
    int n = 0;
    cout << "cin n: ";
    cin >> n;
    cout << "foo1(n): " << foo1(n) << endl;
    cout << "foo2(n): " << foo2(n) << endl;
}