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