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