#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int l[n];
  for (int i = 0; i < n; i++) cin >> l[i];
  int a = 0, b = 0, c = 0;
  for (int i = 0; i < n; i++) {
    if (i % 3 == 0)
      a += l[i];
    else if (i % 3 == 1)
      b += l[i];
    else
      c += l[i];
  }
  string s;
  if (a == max(max(a, b), c))
    s = "chest";
  else if (b == max(max(a, b), c))
    s = "biceps";
  else
    s = "back";
  cout << s;
}
