#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  double r, x1, y1, x2, y2, l, m;
  while (cin >> r >> x1 >> y1 >> x2 >> y2) {
    l = sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
    m = l / (2.0 * r);
    n = m;
    if (l - (2.0 * r) * n > 1e-8) n++;
    cout << n << endl;
  }
  return 0;
}
