#include <bits/stdc++.h>
using namespace std;
pair<int, string> ex[3];
int main() {
  int N;
  scanf("%d", &N);
  int e;
  ex[0] = make_pair(0, "chest");
  ex[1] = make_pair(0, "biceps");
  ex[2] = make_pair(0, "back");
  for (int i = 0; i < N; i++) {
    scanf("%d", &e);
    ex[i % 3].first += e;
  }
  sort(ex, ex + 3);
  cout << ex[2].second << endl;
}
