#include <bits/stdc++.h>
using namespace std;
double distanceBetweenTwoPoints(int x, int y, int a, int b) {
  return sqrt(pow(x - a, 2.0) + pow(y - b, 2.0));
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  int r, x, y, a, b;
  cin >> r >> x >> y >> a >> b;
  double ans = distanceBetweenTwoPoints(x, y, a, b);
  cout << (ceil(ans / (r * 2))) << endl;
}
