#include <bits/stdc++.h>
using namespace std;
int main() {
  int a;
  cin >> a;
  int s[3];
  for (int i = 0; i < 3; i++) s[i] = 0;
  int n[100];
  for (int i = 0; i < a; i++) cin >> n[i];
  for (int i = 0; i < 3; i++)
    for (int j = i; j < a; j = j + 3) {
      s[i] = n[j] + s[i];
    }
  if (s[0] > s[1] && s[0] > s[2])
    cout << "chest";
  else if (s[1] > s[0] && s[1] > s[2])
    cout << "biceps";
  else
    cout << "back";
  return 0;
}
