#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  int t, c = 0, d = 0, e = 0;
  cin >> t;
  int a[t];
  for (int i = 0; i < t; i++) cin >> a[i];
  if (t == 2) {
    c = a[0];
    d = a[1];
  } else if (t == 1)
    c = a[0];
  else {
    for (int i = 0; i < t; i++) {
      if (i % 3 == 0)
        c += a[i];
      else if ((i - 1) % 3 == 0)
        d += a[i];
      else
        e += a[i];
    }
  }
  if (c == max(c, max(d, e)))
    cout << "chest";
  else if (d == max(c, max(d, e)))
    cout << "biceps";
  else
    cout << "back";
}
