#include <bits/stdc++.h>
using namespace std;
int a[3];
string b[3] = {"chest", "biceps", "back"};
int main() {
  ios::sync_with_stdio(true);
  int n;
  cin >> n;
  int x;
  int _max = 0;
  for (int i = 0; i < n; i++) {
    cin >> x;
    a[i % 3] += x;
    if (a[_max] < a[i % 3]) {
      _max = i % 3;
    }
  }
  cout << b[_max] << endl;
  return 0;
}
