#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  if (x == x1 && y == y1) {
    cout << 0 << endl;
    return 0;
  }
  int raiz = ((x1 - x) * (x1 - x)) + ((y1 - y) * (y1 - y));
  raiz = sqrt(raiz);
  cout << raiz / r - 1 << endl;
}
