#include <iostream>
    using namespace std;
    
    // 'const' means *you* can't change the value
    // It does not mean the value cannot change
    
    void f(const int& x, int* y)
    {
        cout << "x = " << x << endl;
        *y = 5;
        cout << "x = " << x << endl;
    }
     
    int main()
    {
        int x = 10;
        f(x, &x);
    }