#include <bits/stdc++.h>
using namespace std;
int main() {
  bool f = 0, ff = 0, fff = 0;
  int n, m1 = 0, m2 = 0, m3 = 0;
  cin >> n;
  for (int j = 0; j < n; ++j) {
    int a;
    cin >> a;
    if (f == 0 && ff == 0 && fff == 0) {
      m1 += a;
      f = 1;
    } else if (f == 1 && ff == 0 && fff == 0) {
      m2 += a;
      ff = 1;
      f = 0;
    } else if (f == 0 && ff == 1 && fff == 0) {
      m3 += a;
      ff = 0;
      f = 0;
    }
  }
  int x = max(m1, max(m2, m3));
  if (x == m1) cout << "chest" << endl;
  if (x == m2) cout << "biceps" << endl;
  if (x == m3) cout << "back" << endl;
}
