#include <string>
#include <deque>
#include <vector>
#include <list>
#include <cmath>
#include <algorithm>
#include <map>
#include <set>
#include <iostream>
#include <cstdio>
#include <cstdlib>
using namespace std;

class GroupTheNumbers {
  public:
    string calculate(vector <int> a);
};

string GroupTheNumbers::calculate(vector <int> a)
{
  return "";
}