#include <bits/stdc++.h>
using namespace std;
int main() {
  double r, x, y, x1, y1;
  double step;
  scanf("%lf %lf %lf %lf %lf", &r, &x, &y, &x1, &y1);
  if (r >= 1 && r <= 100000 && x >= -100000 && x <= 100000 && y >= -100000 &&
      y <= 100000 && x1 >= -100000 && x1 <= 100000 && y1 >= -100000 &&
      y1 <= 100000) {
    step = (sqrt((y - y1) * (y - y1) + (x - x1) * (x - x1))) / (2.0 * r);
    if ((long long)step == step)
      cout << step << endl;
    else
      printf("%d\n", (int)step + 1);
  }
  return 0;
}
