Substitute

#include <iostream>

using namespace std;

int main() {
    int a, b, c, d, counter = 0;
    cin >> a >> b >> c >> d;

    for (int k = a; k < 9; k++) {
        for (int l = 9; l >= b; l--) {
            for (int m = c; m < 9; m++) {
                for (int n = 9; n >= d; n--) {
                    if (k % 2 == 0 && m % 2 == 0 && l % 2 == 1 && n % 2 == 1) {
                        if (k == m && l == n) {
                            cout << "Cannot change the same player.\n";
                        }
                        else {
                            cout << k << l << " - " << m << n << endl;

                            if (++counter == 6) {
                                return 0;
                            }
                        }
                    }
                }
            }
        }
    }
    return 0;
}