#include <bits/stdc++.h>
using namespace std;
void rwf() {}
int32_t main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  rwf();
  long long n;
  cin >> n;
  long long a, chest = 0, biceps = 0, back = 0;
  for (long long i = 1; i <= n; i++) {
    cin >> a;
    if (i % 3 == 0) back += a;
    if (i % 3 == 1) chest += a;
    if (i % 3 == 2) biceps += a;
  }
  long long ans = max(chest, max(biceps, back));
  if (ans == chest)
    cout << "chest";
  else if (ans == biceps)
    cout << "biceps";
  else
    cout << "back";
  return 0;
}
