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