Waiter c++0x

//g++ fun.cpp -std=c++11 -pthread && ./a.out
#include <iostream>
#include <chrono>
#include <thread>
#include <vector>
using namespace std;

class Waiter{
private:
    vector<thread> ts;
public:
    void add(function<void(void)> f){
        ts.push_back(thread(f));
    }

    ~Waiter(){
        for (auto &t: ts){
            t.join();
        }
    }
};

int main()
{
    Waiter w;
    cout << "START\n";
    w.add([] () {  cout << "1 thread\n"; this_thread::sleep_for(chrono::seconds(5)); cout << "1 thread over\n"; });
    w.add([] () {  cout << "2 thread\n"; this_thread::sleep_for(chrono::seconds(3)); cout << "2 thread over\n"; });
    cout << "END\n";
}