#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, x1, y1;
  scanf("%d", &r);
  scanf("%d%d", &x, &y);
  scanf("%d%d", &x1, &y1);
  printf("%d", (int)ceil(hypot(x - x1, y - y1) / (2 * r)));
}
