#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long r, x1, y1, x2, y2, dis = 0;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  dis = ((x1 - x2) * (x1 - x2)) + ((y1 - y2) * (y1 - y2));
  dis = ceil(sqrt((double)dis));
  x1 = dis / (r * 2);
  x2 = dis % (r * 2);
  if (x2 > 0) x1++;
  cout << x1 << "\n";
  return 0;
}
