#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int n;
  cin >> n;
  int a[n];
  int ches = 0, bic = 0, back = 0;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  for (int i = 0; i < n; i++) {
    if (i % 3 == 0)
      ches += a[i];
    else if (i % 3 == 1)
      bic += a[i];
    else
      back += a[i];
  }
  int maxi = INT_MIN;
  maxi = max(ches, bic);
  maxi = max(maxi, back);
  if (maxi == ches)
    cout << "chest" << endl;
  else if (maxi == bic)
    cout << "biceps" << endl;
  else
    cout << "back" << endl;
  return 0;
}
