#include <bits/stdc++.h>
using namespace std;
int n;
int prim[1000006];
double dist(double x, double y, double xt, double yt) {
  return sqrt((x - xt) * (x - xt) + (y - yt) * (y - yt));
}
int main(int argc, char** argv) {
  double r, x, y, xt, yt;
  cin >> r >> x >> y >> xt >> yt;
  double dis = dist(x, y, xt, yt);
  double step = dis / (2 * r);
  int tstep = step;
  if (step > tstep) tstep++;
  cout << tstep << endl;
  return 0;
}
