#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, x;
  cin >> n;
  int sum1 = 0, sum2 = 0, sum3 = 0;
  int k = 1;
  for (int i = 0; i < n; ++i) {
    cin >> x;
    if (k == 4) k = 1;
    switch (k) {
      case 1:
        sum1 += x;
        break;
      case 2:
        sum2 += x;
        break;
      case 3:
        sum3 += x;
        break;
    }
    ++k;
  }
  if (sum1 >= sum2 && sum1 >= sum3)
    cout << "chest";
  else if (sum2 >= sum1 && sum2 >= sum3)
    cout << "biceps";
  else
    cout << "back";
  return 0;
}
