#include <bits/stdc++.h>
using namespace std;
int main() {
  double r, x, y, x1, y1, b;
  double a;
  int c;
  cin >> r >> x >> y >> x1 >> y1;
  a = sqrt((x - x1) * (x - x1) + (y - y1) * (y - y1));
  b = 2 * r;
  c = (int)(a / b);
  if (b * c < a) c++;
  cout << c << endl;
}
