#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:99999999999")
using namespace std;
int main() {
  double x, x1, y1, y;
  int r;
  cin >> r >> x >> y >> x1 >> y1;
  r *= 2;
  double d = (x - x1) * (x - x1) + (y - y1) * (y - y1);
  d = sqrt(d);
  double h = d / r;
  if (double(int(h + 0.0000001)) != h) {
    h = double(int(h)) + 1.0;
  }
  cout << int(h) << endl;
  return 0;
}
