#include <bits/stdc++.h>
using namespace std;
int main() {
  double r, k, x1, x2, y1, y2;
  int p;
  while (cin >> r >> x1 >> y1 >> x2 >> y2) {
    k = sqrt(pow(x2 - x1, 2) + pow(y2 - y1, 2));
    p = k / (2 * r);
    if (k - p * 2 * r != 0) p++;
    cout << p << endl;
  }
}
