#include <bits/stdc++.h>
using namespace std;
int max(int a, int b) {
  if (a > b)
    return a;
  else
    return b;
}
int main() {
  int n;
  cin >> n;
  int ch = 0, bi = 0, ba = 0;
  int t;
  for (int i = 0; i < n; i++) {
    cin >> t;
    if (i % 3 == 0)
      ch = ch + t;
    else if (i % 3 == 1)
      bi = bi + t;
    else
      ba = ba + t;
  }
  if (max(ch, max(bi, ba)) == ch)
    cout << "chest\n";
  else if (max(ch, max(bi, ba)) == bi)
    cout << "biceps\n";
  else
    cout << "back\n";
  return 0;
}
