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