#include <bits/stdc++.h>
using namespace std;
int main() {
  int raio, x, y, x1, y1;
  cin >> raio >> x >> y >> x1 >> y1;
  double diametro = sqrt(pow(y1 - y, 2.0) + pow(x1 - x, 2.0));
  cout << (ceil)(diametro / raio / 2.0) << endl;
  return 0;
}
