#include <bits/stdc++.h>
using namespace std;
int main() {
  long long p, a, b, c, d, r;
  double i, j, k;
  cin >> r >> a >> b >> c >> d;
  p = (a - c) * (a - c) + (b - d) * (b - d);
  k = p * 1.0;
  k = sqrt(k);
  j = 2.0 * r;
  i = k / j;
  a = ceil(i);
  cout << a << endl;
  return 0;
}
