#include <bits/stdc++.h>
using namespace std;
unsigned long int square(unsigned long int x) {
  unsigned long int sq = x * x;
  return sq;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);
  cout.tie(NULL);
  int r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  float n = ceil(sqrt(pow(abs(x1 - x), 2) + pow(abs(y1 - y), 2)) / (2 * r));
  cout << n;
  return 0;
}
