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