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