#include <bits/stdc++.h>
using namespace std;
int main() {
  int arr[1001];
  int n;
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> arr[i];
  }
  int chest = 0, bices = 0, back = 0;
  for (int i = 0; i < n; i++) {
    if (i % 3 == 0) {
      chest += arr[i];
    } else if (i % 3 == 1) {
      bices += arr[i];
    } else {
      back += arr[i];
    }
  }
  if (chest > bices && chest > back) {
    cout << "chest";
  } else if (bices > chest && bices > back) {
    cout << "biceps";
  } else {
    cout << "back";
  }
  return 0;
}
