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