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

class Timer {
private:
    std::chrono::high_resolution_clock::time_point _start, _stop;

public:
    Timer() {
        _start = std::chrono::high_resolution_clock::now();
        _stop = _start;
    }

    void start() {
        _start = std::chrono::high_resolution_clock::now();
    }

    void stop() {
        _stop = std::chrono::high_resolution_clock::now();
    }

    friend ostream& operator<<(ostream& out, Timer& obj) {
	    auto elapsed_ns = std::chrono::duration_cast<std::chrono::nanoseconds>(obj._stop - obj._start);
        auto elapsed_ms = std::chrono::duration_cast<std::chrono::milliseconds>(obj._stop - obj._start);
        auto elapsed_s = elapsed_ms.count() / 1000.0;
        out << "time_ns=" << elapsed_ns.count() << endl;
        out << "time_ms=" << elapsed_ns.count() << endl;
        out << "time_s=" << setprecision(3) << elapsed_s << endl;
        return out;
    }
};