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