#include <bits/stdc++.h>
using namespace std;
int main(void) {
  int i;
  cin >> i;
  vector<int> data(i);
  for (i = 0; i < data.size(); i++) {
    cin >> data[i];
  }
  vector<int> res(3);
  for (i = 0; i < data.size(); i++) {
    res[i % 3] += data[i];
  }
  int max = -1;
  int in = -1;
  for (i = 0; i < 3; i++) {
    if (res[i] > max) {
      max = res[i];
      in = i;
    }
  }
  if (in == 0)
    cout << "chest" << endl;
  else if (in == 1)
    cout << "biceps" << endl;
  else
    cout << "back" << endl;
  return 0;
}
