#include <bits/stdc++.h>
using namespace std;
int r;
double x, y, _x, _y;
int main() {
  cin >> r >> x >> y >> _x >> _y;
  double d = sqrt((x - _x) * (x - _x) + (y - _y) * (y - _y));
  cout << ceil(d / (2 * r)) << endl;
  return 0;
}
