#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  scanf("%d", &n);
  int i = 0;
  int A[3] = {0};
  while (n--) {
    int f;
    scanf("%d", &f);
    A[i % 3] += (f);
    i++;
  }
  if (A[0] > A[1] && A[0] > A[2])
    cout << "chest";
  else if (A[1] > A[2] && A[1] > A[0])
    cout << "biceps";
  else
    cout << "back";
}
