#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  long long int p = pow((x1 - x2), 2) + pow((y1 - y2), 2);
  double dist = sqrt((double)p);
  double fraction = (double)dist / (2 * r);
  int ans = ceil(fraction);
  cout << ans << endl;
  return 0;
}
