#include <bits/stdc++.h>
using namespace std;
struct abc {
  long long int x, y;
};
bool compare(abc a1, abc a2) {
  if (a1.x == a2.x) return a1.y > a2.y;
  return a1.x < a2.x;
}
const long long int mod = 1e9 + 7;
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  ;
  long long int r;
  long double x, y, a, b;
  cin >> r >> x >> y >> a >> b;
  long double p = sqrt((x - a) * (x - a) + (y - b) * (y - b));
  cout << ceil(p / (2 * r));
}
