#include <iostream>
#include <future>
#include <chrono>
using namespace std;

int main() {
	auto start = chrono::system_clock::now();
	auto f = async(launch::async, [=](){
		this_thread::sleep_for(chrono::seconds(3));
	});
	chrono::duration<double> diff = chrono::system_clock::now() - start;
	cout << "Elapsed " << diff.count() << " seconds" << endl;
	return 0;
}