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