#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int r, x, y, x1, y1, ans;
  cin >> r >> x >> y >> x1 >> y1;
  double t = sqrt((x1 - x) * (x1 - x) * 1.00 + (y1 - y) * (y1 - y) * 1.00);
  ans = ceil(double(t) / (2 * r));
  cout << ans << endl;
  return 0;
}
