#include <bits/stdc++.h>
using namespace std;
int main() {
  int x1, y1, x2, y2;
  double r;
  scanf("%lf%d%d%d%d", &r, &x1, &y1, &x2, &y2);
  double dis = sqrt(pow(x2 - x1, 2.0) + pow(y2 - y1, 2.0));
  cout << ceil(dis / (2.0 * r)) << endl;
  return 0;
}
