#include <bits/stdc++.h>
using namespace std;
int p[111];
int main() {
  int n, a = 0, b = 0, c = 0;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> p[i];
    if (i < 3 && i == 1 || i % 3 == 1) {
      a = a + p[i];
    } else if (i < 3 && i == 2 || i % 3 == 2) {
      b = b + p[i];
    } else if (i % 3 == 0) {
      c = c + p[i];
    }
  }
  if (max(a, max(b, c)) == a) {
    cout << "chest";
  } else if (max(a, max(b, c)) == b) {
    cout << "biceps";
  } else if (max(a, max(b, c)) == c) {
    cout << "back";
  }
}
