#include <bits/stdc++.h>
using namespace std;
bool is_prime(long long n) {
  if (n == 2) return true;
  if (n % 2 == 0) return false;
  if (n < 2) return true;
  for (long long i = 3; i * i <= n; i += 2)
    if (n % i == 0) return false;
  return true;
}
int main() {
  int x1, x2, y1, y2, r;
  double d;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  d = sqrt(pow(abs(y2 - y1), 2) + pow(abs(x2 - x1), 2));
  double output = d / (2 * r);
  double moves = ceil(output);
  cout << (int)moves;
  return 0;
}
