#include <iostream>
#include <future>
#include <chrono>
using namespace std;
int main() {
auto start = chrono::system_clock::now();
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;
}
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