#include <bits/stdc++.h>
using namespace std;
using lli = long long int;
const unsigned int M = 1000000007;
int main() {
  lli r, x, x1, y, y1;
  cin >> r >> x >> y >> x1 >> y1;
  double d = (x1 - x) * (x1 - x) + (y1 - y) * (y1 - y);
  d = sqrt(d);
  double res = ceil(d / (2 * r));
  cout << res << "\n";
  return 0;
}
