#include <bits/stdc++.h>
using namespace std;
int arr[3];
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int t;
  cin >> t;
  for (int i = 0; i < t; ++i) {
    int x;
    cin >> x;
    arr[i % 3] += x;
  }
  int count = 0;
  for (int i = 0; i < 3; i++) {
    count = max(count, arr[i]);
  }
  if (arr[0] == count) {
    cout << "chest"
         << "\n";
  }
  if (arr[1] == count) {
    cout << "biceps"
         << "\n";
  }
  if (arr[2] == count) {
    cout << "back"
         << "\n";
  }
  return 0;
}
