#include <bits/stdc++.h>
using namespace std;
long long gcd(long long a, long long b) {
  while (b != 0) {
    int t = b;
    b = a % b;
    a = t;
  }
  return a;
}
long long lcm(long long x, long long y) {
  long long z;
  z = x * y / gcd(x, y);
  return z;
}
bool prime(long long num) {
  if (num <= 1) return false;
  if (num == 2 || num == 3) return true;
  if (num % 2 == 0 || num % 3 == 0) return false;
  for (long long i = 3; i * i <= num; i += 2)
    if (num % i == 0) return false;
  return true;
}
unsigned long long power2(int num) {
  unsigned long long sum = 1;
  for (int i = 0; i < num; i++) sum *= 2;
  return sum;
}
unsigned long long power(long long n, long long b) {
  unsigned long long sum = 1;
  for (int i = 0; i < b; i++) {
    sum *= n;
    sum %= (1000000000 + 7);
  }
  return sum;
}
void f() {
  std::ios_base::sync_with_stdio(0);
  cin.tie(NULL);
  cout.tie(NULL);
}
#pragma warning(disable : 4996)
void in_out_txt() {
  freopen("input.txt", "rt", stdin);
  freopen("output.txt", "wt", stdout);
}
void FillArray(int arr[], int n, int num) {
  for (int i = 0; i < n; i++) arr[i] = num;
}
int main() {
  f();
  pair<int, string> pr[3];
  pr[0].second = "chest", pr[1].second = "biceps", pr[2].second = "back";
  int n;
  cin >> n;
  int x;
  int y;
  for (int i = 0; i < n; i++) {
    cin >> x;
    y = i % 3;
    pr[y].first += x;
  }
  sort(pr, pr + 3);
  cout << pr[2].second << endl;
  return 0;
}
