#include <bits/stdc++.h>
using namespace std;
long int square(int x) { return x * x; }
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 d = (float)sqrt(square(x1 - x) + square(y1 - y));
  cout << ceil(d / (2 * r));
  return 0;
}
