#include <iostream>
#include <string>
#include "hwrld.h"


int main() {
    std::string a = "Hello,", b = "World!";
    std::cout << concat(a, b) << std::endl;
    std::vector<int> is = {1, 2, 3, 4};
    std::cout << sum_of_ints(is) << std::endl;
}