Determining the weight of a non-fake coin in constant time

fakecoin1.cpp

#include <iostream>
#include <vector>
using namespace std;

int weigh(int w1, int w2) {
    cout << "WEIGHING EVENT" << endl;
    return w1 - w2;
}

int main()
{
    int n;
    cout << "Number of coins (min = 3): ";
    cin >> n;

    vector<int> v(n);

    for(int i = 0; i < n; i++) {
        cout << "Coin #" << (i + 1) << " weight: ";
        cin >> v[i];
    }

    int good_weight = v[0];
    bool heavier = false;

    if(weigh(v[0], v[1]) != 0) {
        if(weigh(v[0], v[2]) != 0) {
            good_weight = v[1];
        }
    }

    cout << "The non-counterfeit weight is: " << good_weight << endl;

    return 0;
}