#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int c1 = 0, c2 = 0, c3 = 0;
  int arr[n];
  for (int i = 1; i <= n; i++) {
    cin >> arr[i];
    if (i % 3 == 1) c1 += arr[i];
    if (i % 3 == 2) c2 += arr[i];
    if (i % 3 == 0) c3 += arr[i];
  }
  if (c1 == max(c1, max(c2, c3))) {
    cout << "chest";
  } else if (c2 == max(c1, max(c2, c3))) {
    cout << "biceps";
  } else if (c3 == max(c1, max(c2, c3))) {
    cout << "back";
  }
}
