#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int rep[n + 1];
  for (int x = 1; x <= n; x++) cin >> rep[x];
  int chest(0), biceps(0), back1(0);
  for (int x = 1; x <= n; x++) {
    if (x % 3 == 1) chest += rep[x];
    if (x % 3 == 2) biceps += rep[x];
    if (x % 3 == 0) back1 += rep[x];
  }
  int maxtrain = max(chest, max(biceps, back1));
  if (maxtrain == chest) cout << "chest";
  if (maxtrain == biceps) cout << "biceps";
  if (maxtrain == back1) cout << "back";
  return 0;
}
