#include <bits/stdc++.h>
using namespace std;
double r, x1, yy, x2, y2;
int main() {
  cin >> r >> x1 >> yy >> x2 >> y2;
  double res;
  res = sqrt((x1 - x2) * (x1 - x2) + (yy - y2) * (yy - y2)) / (2 * r);
  int ress = ceil(res);
  cout << ress;
  return 0;
}
