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