#include <iostream>

// Function prototypes
void func1(ostream& out, int& x, int y);
void func2(ostream& out, int x, int y);
void func3(ostream& out, const int& x, int& y);

void main() {
    int x = 10;
    int y = 20;

    func1(cout, y, x);
    cout << "main: " << x << ' ' << y << endl;
}

void func1(ostream& out, int& x, int y) {
    func3(out, x, y);

    out << "func1: " << x << ' ' << y << endl;
}

void func2(ostream& out, int x, int y) {
    x = 2 * x;
    y = 3 * y;

    out << "func2: " << x << ' ' << y << endl;   
}

void func3(ostream& out, const int& x, int& y) {
    y = x + 2;

    func2(out, y, x);

    out << "func3: " << x << ' ' << y << endl;    
}

-------------------------------------------------
Answer:

func2: 44 60
func3: 20 22
func1: 20 22
main: 10 20