#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);
  long long r, x1, y1, x2, y2;
  long double d;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  d = sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
  long double a = d / (2 * r);
  long long ans = ceil(a);
  cout << ans << endl;
  return 0;
}
