#include <bits/stdc++.h>
int main() {
  long long int x, x1, y, y1, r, ans;
  double dis;
  scanf("%lld %lld %lld %lld %lld", &r, &x, &y, &x1, &y1);
  dis = (sqrt(pow(x - x1, 2.0) + pow(y + y1, 2.0))) / (2 * r);
  ans = ceil(dis);
  printf("%lld\n", ans);
  return 0;
}
