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