#include <cstdio>
#include <vector>
#include <list>
#include <set>
#include <unordered_set>

using namespace std;

int main(int argc, char* argv[])
{
  
  //vector<int> x;
  //list<int> x;
  set<int> x;
  //unordered_set<int> x;

  printf("size: %lu\n", x.size());

  for(int i = 0; i < 20; i++){
    //x.push_back(i * i);
    x.insert(i * i);
  }

  printf("size: %lu\n", x.size());

  for(auto it = x.begin(); it != x.end(); it++){
    printf("%d, ", *it);
  }

//  for(list<int>::reverse_iterator it = x.rbegin(); it != x.rend(); it++){
//    printf("%d, ", *it);
//  }


  return 0;
}