What will be the output of the following C++ code?

#include <iostream>
using namespace std;
class numbers
{
    private:
    int m_nValues[10];
    public:
    int& operator[] (const int nValue);
};
int& numbers::operator[](const int nValue)
{
    return m_nValues[nValue];
}
int main()
{
    numbers N;
    N[5] = 4;
    cout <<  N[5];
    return 0;
}