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