#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  int xx = x - x1;
  int yy = y - y1;
  int d = ceil(sqrt(pow(xx, 2) + pow(yy, 2)));
  d /= 2 * r;
  cout << d;
  return 0;
}
