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

int main () {
  using std::unordered_map;
  using std::string;

    unordered_map<string, int> employeeTable;
    unordered_map<string, int>::iterator it;

    employeeTable["hello"] = 4;
    employeeTable["goodbye"] = 2;
    employeeTable["Hello, again"] = 27;

    std::cout << employeeTable.size() << "\n";

    for (it = employeeTable.begin(); it != employeeTable.end();) {
       int age = it->second;
       if (age < 18) {
          employeeTable.erase(it++); // <== FAILS HERE!!!!!!
       } else {
          ++it;
       }
    }

    std::cout << employeeTable.size() << "\n";

}