#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, c = 0, b = 0, bi = 0, t, j;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> t;
    j = i % 3;
    if (j == 1)
      c += t;
    else if (j == 2)
      bi += t;
    else
      b += t;
  }
  t = max(b, max(bi, c));
  if (t == b)
    cout << "back" << endl;
  else if (t == bi)
    cout << "biceps" << endl;
  else
    cout << "chest" << endl;
  return 0;
}
