#include <bits/stdc++.h>
using namespace std;
string s[] = {"chest", "biceps", "back"};
int a[30], b[30], n;
int main() {
  cin >> n;
  for (int i = 0; i < n; i++) cin >> a[i];
  for (int i = 0; i < n; i++) b[i % 3] += a[i];
  int p = 0;
  if (b[1] > b[p]) p = 1;
  if (b[2] > b[p]) p = 2;
  cout << s[p] << endl;
  return 0;
}
