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