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