#include <string>
#include <iostream>
#include <unordered_map>

using namespace std;

void fun(int& val)
{

    cout << val << endl;
    val = 900;
}

int main()
{      
    std::unordered_map<std::string, int> test;
    fun(test["hello"]);

    cout << test["hello"] << endl;

}