#include <bits/stdc++.h>
using namespace std;
double n, x, y, x2, y2, c;
int main() {
  scanf("%lf%lf%lf%lf%lf", &n, &x, &y, &x2, &y2);
  c = ceil(sqrt(pow((x - x2), 2) + pow((y - y2), 2)) / (2 * n));
  printf("%.0lf", c);
  return 0;
}
