#include <bits/stdc++.h>
using namespace std;
int main() {
  double r, x, y, x1, y1, s, n;
  cin >> r >> x >> y >> x1 >> y1;
  s = sqrt((x - x1) * (x - x1) + (y - y1) * (y - y1)) - 2 * r;
  if (x == x1 && y == y1)
    cout << 0 << endl;
  else if (s <= 0)
    cout << 1 << endl;
  else {
    n = s / (2 * r);
    if (s / (2 * r))
      cout << (int)n + 2 << endl;
    else
      cout << (int)n + 1 << endl;
  }
  return 0;
}
