#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, sum_chest = 0, sum_biceps = 0, sum_back = 0, t;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    if (i % 3 == 1) {
      cin >> t;
      sum_chest += t;
    }
    if (i % 3 == 2) {
      cin >> t;
      sum_biceps += t;
    }
    if (i % 3 == 0) {
      cin >> t;
      sum_back += t;
    }
  }
  if (sum_chest > sum_biceps and sum_chest > sum_back)
    cout << "chest" << endl;
  else if (sum_biceps > sum_chest and sum_biceps > sum_back)
    cout << "biceps" << endl;
  else
    cout << "back" << endl;
  return 0;
}
