#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int a[n];
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  int s1 = 0, s2 = 0, s3 = 0;
  if (n > 3) {
    for (int i = 0; i < n; i += 3) {
      s1 += a[i];
    }
    for (int i = 0; i < n - 1; i += 3) {
      s2 += a[i + 1];
    }
    for (int i = 0; i < n - 2; i += 3) {
      s3 += a[i + 2];
    }
  } else if (n == 2) {
    s1 = a[0];
    s2 = a[1];
  } else if (n == 1) {
    s1 = a[0];
  } else if (n == 3) {
    s1 = a[0];
    s2 = a[1];
    s3 = a[2];
  }
  if (s1 > s2 && s1 > s3)
    cout << "chest";
  else if (s2 > s1 && s2 > s3)
    cout << "biceps";
  else if (s3 > s1 && s3 > s2)
    cout << "back";
  return 0;
}
