#include <bits/stdc++.h>
using namespace std;
const long long MXN = 1e5 + 7;
int main() {
  long long a[MXN], n, cnt1 = 0, cnt3 = 0, cnt2 = 0;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> a[i];
  }
  for (int i = 1; i <= n; i++) {
    if (i % 3 == 1) {
      cnt1 += a[i + 1];
    }
    if (i % 3 == 1 || i == 1) {
      cnt2 += a[i];
    }
    if (i % 3 == 0) {
      cnt3 += a[i];
    }
  }
  if (cnt1 == max(cnt1, max(cnt2, cnt3))) {
    cout << "biceps";
  } else if (cnt2 == max(cnt1, max(cnt2, cnt3))) {
    cout << "chest";
  } else {
    cout << "back";
  }
  exit(0);
}
