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