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