#include <bits/stdc++.h>
using namespace std;
int n;
int a[25];
int s, s2, s3;
int main() {
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
    if (i % 3 == 0)
      s += a[i];
    else if (i % 3 == 1)
      s2 += a[i];
    else if (i % 3 == 2)
      s3 += a[i];
  }
  if (max(max(s, s2), s3) == s)
    cout << "chest";
  else if (max(max(s, s2), s3) == s2)
    cout << "biceps";
  else if (max(max(s, s2), s3) == s3)
    cout << "back";
}
