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