#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int n, a;
  vector<pair<int, string> > muscle;
  while (cin >> n) {
    muscle.assign(3, pair<int, string>());
    muscle[0].second = "chest";
    muscle[1].second = "biceps";
    muscle[2].second = "back";
    for (int i = 0; i < n; ++i) {
      cin >> a;
      muscle[i % 3].first += a;
    }
    cout << (*max_element(muscle.begin(), muscle.end())).second << endl;
  }
  return 0;
}
