#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, a[5] = {}, x, mx = -1, cur = 0;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> x;
    if (i == 1 || i % 3 == 1)
      a[1] += x;
    else if (i == 2 || i % 3 == 2) {
      a[2] += x;
    } else if (i == 3 || i % 3 == 0)
      a[3] += x;
  }
  for (int i = 1; i <= 3; i++) {
    if (a[i] > mx) {
      mx = a[i];
      cur = i;
    }
  }
  if (cur == 1)
    cout << "chest";
  else if (cur == 2)
    cout << "biceps";
  else
    cout << "back";
  return 0;
}
