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