#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, a = 0, b = 0, c = 0, t;
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> t;
    if (i % 3 == 0)
      a += t;
    else if (i % 3 == 1)
      b += t;
    else
      c += t;
  }
  string s;
  s = a > b ? (a > c ? "chest" : "back") : (b > c ? "biceps" : "back");
  cout << s << endl;
  return 0;
}
