#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int* a = new int[n];
  int f[3] = {0, 0, 0};
  for (int i = 0; i < n; ++i) {
    cin >> a[i];
    f[i % 3] += a[i];
  }
  int max1 = max(f[0], max(f[1], f[2]));
  if (max1 == f[0]) cout << "chest";
  if (max1 == f[1]) cout << "biceps";
  if (max1 == f[2]) cout << "back";
}
