#include <bits/stdc++.h>
int main() {
  int n;
  std::cin >> n;
  int f[20];
  for (int i = 0; i < n; ++i) std::cin >> f[i];
  int a = 0, b = 0, c = 0;
  for (int i = 0; i < n; ++i) {
    if (i % 3 == 0) a += f[i];
    if (i % 3 == 1) b += f[i];
    if (i % 3 == 2) c += f[i];
  }
  if (a > b && a > c)
    std::cout << "chest";
  else if (b > a && b > c)
    std::cout << "biceps";
  else
    std::cout << "back";
  return 0;
}
