#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  double d = sqrt(pow(abs(x - x1), 2) + pow(abs(y - y1), 2));
  double res = (double)d / (2.0 * r);
  int x2 = res;
  if (x2 == res)
    cout << x2;
  else
    cout << x2 + 1;
}
