#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  int i;
  int numbers[3];
  int input;
  cin >> n;
  numbers[0] = 0;
  numbers[1] = 0;
  numbers[2] = 0;
  for (i = 0; i < n; i++) {
    cin >> input;
    numbers[i % 3] += input;
  }
  if (numbers[0] > numbers[1] && numbers[0] > numbers[2]) {
    cout << "chest" << endl;
  }
  if (numbers[1] > numbers[0] && numbers[1] > numbers[2]) {
    cout << "biceps" << endl;
  }
  if (numbers[2] > numbers[1] && numbers[2] > numbers[0]) {
    cout << "back" << endl;
  }
  return 0;
}
