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