#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, chest = 0, biceps = 0, back = 0;
  cin >> n;
  vector<int> v(n);
  vector<pair<int, string> > vv;
  for (int i = 0; i < n; i++) {
    cin >> v[i];
  }
  for (int i = 0, s = 0, l = 1, k = 2; i < n; i++) {
    if (i == s) {
      chest += v[i];
      s += 3;
    } else if (i == l) {
      biceps += v[i];
      l += 3;
    } else if (i == k) {
      back += v[i];
      k += 3;
    }
  }
  vv.push_back(make_pair(chest, "chest"));
  vv.push_back(make_pair(biceps, "biceps"));
  vv.push_back(make_pair(back, "back"));
  sort(vv.begin(), vv.end());
  vector<pair<int, string> >::iterator it = vv.end() - 1;
  cout << it->second;
  return 0;
}
