#include <bits/stdc++.h>
using namespace std;
int main() {
  long long r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  double count = sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1)) / (2 * r);
  if ((int)count == count)
    cout << (int)count;
  else
    cout << (int)count + 1;
}
