Crow unordered_map Quiz, C++ (clang)

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//clang 3.8.0

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

int main()
{
    //Create map that has string keys and double values
    std::unordered_map<std::string, double> grades;
    //assign values to keys
    //format: unordered_map[key] = value
    grades["Project 1"] = 94.5;
    grades["Quiz 1"] = 63.75;
    grades["Homework 1"] = 100;
    
    //pulling a specific value from the map
    std::cout << "---Showing how to retrieve a value" << std::endl;
    std::string assignment = "Project 1";
    std::cout << "You got a " << grades[assignment] << " on " << assignment << std::endl;
    
    //detecting if an item is in the map
    std::cout << "---Showing how to check if a key exists" << std::endl;
    assignment = "Project 2";
    bool hasKey = !(grades.find(assignment) == grades.end());
    std::cout << "You have received a grade on " << assignment << ": " << hasKey << std::endl; //There is no "Project 2" key
    
    //Looping through the map
    std::cout << "---Showing how to print all values" << std::endl;
    double sum = 0;
    auto it = grades.begin();
    for(; it != grades.end(); it++)
    {
        std::cout << "You received a " << (it->second) << " on " << (it->first) << std::endl;
        sum += it->second;
    }
    std::cout << "You got a " << (sum/grades.size()) << " average." << std::endl;
}

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Compilation time: 1.74 sec, absolute running time: 0.22 sec, cpu time: 0.12 sec, memory peak: 3 Mb, absolute service time: 1,96 sec