#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  long long xk = (x1 - x2) * (x1 - x2);
  long long yk = (y1 - y2) * (y1 - y2);
  double td = sqrt(xk + yk);
  double nm = td / (r * 2);
  nm += 0.99999999999;
  int vas = (int)nm;
  cout << vas << endl;
}
