#include <iostream>
using namespace std;

class Example {
public:
    int x;
    int GetX() const { // GetX is a constant member function
    	x = x + 1; // This causes an error
    	return x;
    }
};

int main() {
	Example y;
	y.x = 5;
	
	std::cout << y.GetX() << std::endl;

	return 0;
}