#include <bits/stdc++.h>
using namespace std;
const long long mod = 1000000007;
const long long mod2 = 998244353;
const long double pi = 3.1415926535;
const long long MAX = -100000000000;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long n, x = 0, k = 0, f = 0, y = 0, e, m;
  long long a, b;
  cin >> n;
  long long arr[n];
  for (long long i = 0; i < n; i++) cin >> arr[i];
  long long chest = 0, biceps = 0, back = 0;
  for (long long i = 0; i < n; i++) {
    if (i % 3 == 0)
      chest += arr[i];
    else if (i % 3 == 1)
      biceps += arr[i];
    else
      back += arr[i];
  }
  long long mx = max(chest, biceps);
  mx = max(mx, back);
  if (mx == chest)
    cout << "chest";
  else if (mx == biceps)
    cout << "biceps";
  else
    cout << "back";
  return 0;
}
