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