#include <bits/stdc++.h>
using namespace std;
template <typename t>
istream &operator>>(istream &cin, vector<t> &v1) {
  for (auto &i : v1) cin >> i;
  return cin;
}
template <typename t>
ostream &operator<<(ostream &cout, vector<t> &v1) {
  for (auto &i : v1) cout << i << " ";
  return cout;
}
int main() {
  int t = 1;
  while (t--) {
    long long int n, i, max = -1, idx, chest = 0, biceps = 0, back = 0;
    cin >> n;
    long long int arr[n];
    for (i = 0; i < n; i++) {
      cin >> arr[i];
      if (i % 3 == 0)
        chest += arr[i];
      else if (i % 3 == 1)
        biceps += arr[i];
      else
        back += arr[i];
    }
    if (chest > back && chest > biceps)
      cout << "chest";
    else if (back > chest && back > biceps)
      cout << "back";
    else
      cout << "biceps";
  }
  return 0;
}
