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