#include <bits/stdc++.h>
using namespace std;
int mostFrequent(int arr[], int n) {
  sort(arr, arr + n);
  int max_count = 1, res = arr[0], curr_count = 1;
  for (int i = 1; i < n; i++) {
    if (arr[i] == arr[i - 1])
      curr_count++;
    else {
      if (curr_count > max_count) {
        max_count = curr_count;
        res = arr[i - 1];
      }
      curr_count = 1;
    }
  }
  if (curr_count > max_count) {
    max_count = curr_count;
    res = arr[n - 1];
  }
  return res;
}
unsigned int countDivisors(unsigned int n) {
  int cnt = 0;
  for (int i = 1; i <= sqrt(n); i++) {
    if (n % i == 0) {
      if (n / i == i)
        cnt++;
      else
        cnt = cnt + 2;
    }
  }
  return cnt;
}
int main() {
  int n, a;
  long long int back = 0, biceps = 0, chest = 0;
  cin >> n;
  for (int i = 1; i <= (n); ++i) {
    cin >> a;
    if (i % 3 == 0) {
      back += a;
    } else if (i % 3 == 1) {
      chest += a;
    } else if (i % 3 == 2) {
      biceps += a;
    }
  }
  long long int maxi = max(back, max(biceps, chest));
  if (maxi == back)
    cout << "back";
  else if (maxi == biceps)
    cout << "biceps";
  else if (maxi == chest)
    cout << "chest";
  return 0;
}
