#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  int n;
  cin >> n;
  int sum1 = 0, sum2 = 0, sum3 = 0;
  int flag1 = 1, flag2 = 0, flag3 = 0;
  for (int i = 1; i <= n; i++) {
    int a;
    cin >> a;
    if (flag1) {
      sum1 += a;
      flag1 = 0;
      flag2 = 1;
      continue;
    }
    if (flag2) {
      sum2 += a;
      flag2 = 0;
      flag3 = 1;
      continue;
    }
    if (flag3) {
      sum3 += a;
      flag3 = 0;
      flag1 = 1;
      continue;
    }
  }
  if (sum1 > sum2 && sum1 > sum3) {
    cout << "chest\n";
  } else if (sum2 > sum1 && sum2 > sum3) {
    cout << "biceps\n";
  } else {
    cout << "back\n";
  }
  return 0;
}
