#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, c = 1, m, m1 = 0, m2 = 0, m3 = 0;
  cin >> n;
  while (n--) {
    cin >> m;
    if (c == 1)
      m1 += m;
    else if (c == 2)
      m2 += m;
    else
      m3 += m;
    c = (c + 1) % 3;
  }
  m = (m1 > m2 ? (m1 > m3 ? m1 : m3) : (m2 > m3 ? m2 : m3));
  if (m == m1)
    cout << "chest" << endl;
  else if (m == m2)
    cout << "biceps" << endl;
  else
    cout << "back" << endl;
}
