#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, s1 = 0, s2 = 0, s3 = 0;
  cin >> n;
  int a[n];
  for (int i = 0; i < n; i++) {
    cin >> a[i];
    if (i % 3 == 0)
      s1 += a[i];
    else if (i % 3 == 1)
      s2 += a[i];
    else
      s3 += a[i];
  }
  if (s1 >= s2 && s1 >= s3)
    cout << "chest\n";
  else if (s2 >= s3 && s2 >= s1)
    cout << "biceps\n";
  else
    cout << "back\n";
  return 0;
}
