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