#include <bits/stdc++.h>
using namespace std;
const double eps = 1e-13;
bool egal(double a, double b) { return (abs(a - b) < eps); }
double dist(double x, double y, double x1, double y1) {
  return sqrt((x - x1) * (x - x1) + (y - y1) * (y - y1));
}
int main() {
  long long r, x, y, xp, yp;
  cin >> r >> x >> y >> xp >> yp;
  double d = dist(x, y, xp, yp);
  double ans = d / (2 * r);
  long long ans2 = (long long)ans;
  if (egal(ans, ans2))
    ;
  else
    ans2++;
  cout << ans2 << '\n';
  return 0;
}
