#include <bits/stdc++.h>
using namespace std;
int n, t, a[40000];
int main() {
  int r, x1, x2, y1, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  double s = sqrt(abs(x1 - x2) * abs(x1 - x2) + abs(y1 - y2) * abs(y1 - y2));
  int k = s / (r * 2);
  if (fmod(s, (r * 2)) != 0) k++;
  cout << k << endl;
  return 0;
}
