#include <bits/stdc++.h>
using namespace std;
const int INF = 0x3f3f3f3f;
int main() {
  long long r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  cout << ceil((double)sqrt((x - x1) * (x - x1) + (y - y1) * (y - y1)) /
               (2 * r))
       << "\n";
}
