#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  int t = 0;
  int a, b, c, d;
  a = x - x1;
  a *= a;
  b = y - y1;
  b *= b;
  c = a + b;
  c = sqrt(c);
  t = ceil(c / (2 * r));
  cout << t;
  return 0;
}
