#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  if ((x) == (x1) and (y1) == (y))
    cout << "0\n";
  else {
    long long int c = 0;
    double dis = sqrt(((x - x1) * (x - x1) + (y - y1) * (y - y1)));
    dis = ceil(dis);
    while (2 * r <= dis) {
      c++;
      dis -= 2 * r;
    }
    if (dis != 0) c++;
    cout << c << endl;
  }
  return 0;
}
