#include <bits/stdc++.h>
int main(int argc, char* argv[]) {
  int r, x1, y1, x2, y2;
  scanf("%d%d%d%d%d", &r, &x1, &y1, &x2, &y2);
  double y = y2 - y1, x = x2 - x1;
  double dist = sqrt(x * x + y * y);
  int ans = int(ceil(dist / r / 2.0));
  printf("%d\n", ans);
  return 0;
}
