#include <bits/stdc++.h>
using namespace std;
int ans1 = 0, ans2 = 0, ans3 = 0, a[100];
int main() {
  int n;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> a[i];
    if (i % 3 == 1) ans1 += a[i];
    if (i % 3 == 2) ans2 += a[i];
    if (i % 3 == 0) ans3 += a[i];
  }
  if (ans1 >= ans2 && ans1 >= ans3) {
    cout << "chest" << endl;
    return 0;
  }
  if (ans2 >= ans1 && ans2 >= ans3) {
    cout << "biceps" << endl;
    return 0;
  }
  if (ans3 >= ans1 && ans3 >= ans2) {
    cout << "back" << endl;
    return 0;
  }
  return 0;
}
