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