#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, z, w;
  cin >> r >> x >> y >> z >> w;
  if (x == z && y == w) {
    cout << "0\n";
    return 0;
  }
  int dist = (z - x) * (z - x) + (w - y) * (w - y);
  dist = (int)sqrt((double)dist);
  dist /= r;
  cout << --dist << endl;
}
