#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x2, y2, x1, y1, sum = 0;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  double dist = sqrt(pow(x2 - x1, 2) + pow(y2 - y1, 2));
  int k = r * 2;
  sum = dist / k;
  if (dist > sum * k) sum++;
  cout << sum;
  return 0;
}
