#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int a[n + 10];
  int exercise1 = 0, exercise2 = 0, exercise3 = 0;
  for (int i = 1; i <= n; i++) {
    cin >> a[i];
  }
  for (int i = 1; i <= n; i += 3) {
    exercise1 += a[i];
  }
  for (int i = 2; i <= n; i += 3) {
    exercise2 += a[i];
  }
  for (int i = 3; i <= n; i += 3) {
    exercise3 += a[i];
  }
  if (exercise1 > exercise2) {
    if (exercise1 > exercise3) {
      cout << "chest";
    } else {
      cout << "back";
    }
  } else {
    if (exercise2 > exercise3) {
      cout << "biceps";
    } else {
      cout << "back";
    }
  }
}
