#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int arr[3] = {0};
  int t;
  int tmp[21];
  for (int i = 1; i <= n; i++) cin >> tmp[i];
  for (int i = 1; i <= n; i += 3) {
    arr[0] += tmp[i];
  }
  for (int i = 2; i <= n; i += 3) {
    arr[1] += tmp[i];
  }
  for (int i = 3; i <= n; i += 3) {
    arr[2] += tmp[i];
  }
  if (max(arr[0], max(arr[1], arr[2])) == arr[0])
    cout << "chest";
  else if (max(arr[0], max(arr[1], arr[2])) == arr[1])
    cout << "biceps";
  else
    cout << "back";
  return 0;
}
