#include <bits/stdc++.h>
char muscle[][16] = {"chest", "biceps", "back"};
int cnt[4];
int main() {
  int n;
  scanf("%d", &n);
  for (int i = 0; i < n; ++i) {
    int k;
    scanf("%d", &k);
    cnt[i % 3] += k;
  }
  if (cnt[0] > cnt[1] && cnt[0] > cnt[2])
    puts(muscle[0]);
  else if (cnt[1] > cnt[2])
    puts(muscle[1]);
  else
    puts(muscle[2]);
  return 0;
}
