#include <bits/stdc++.h>
using namespace std;
int main() {
  double r, x, y, a, b;
  scanf("%lf%lf%lf%lf%lf", &r, &x, &y, &a, &b);
  double p = 1.0;
  double dis = p * (a - x) * (a - x) + p * (b - y) * (b - y);
  dis = sqrt(dis);
  long m;
  dis = dis / (2 * r);
  m = (long)dis;
  if (dis == m * p)
    printf("%ld", m);
  else
    printf("%ld", m + 1);
  return 0;
}
