#include <bits/stdc++.h>
using namespace std;
const long long N = 3e6 + 7, M = 1e7 + 7, inf = 1e9 + 123, mod = 1e9 + 7,
                key = 31;
template <typename T>
inline T sqr(T t) {
  return t * t;
}
inline void file() {
  cout.precision(5);
  cout << fixed;
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
}
struct point {
  int x, y;
};
point a, b;
int n, m, k, x, ans, r;
int main() {
  file();
  cin >> r >> a.x >> a.y >> b.x >> b.y;
  double dist = sqrt((a.x - b.x) * (a.x - b.x) + (a.y - b.y) * (a.y - b.y));
  r = r * 2;
  while (dist > 0) {
    dist -= r;
    ans++;
  }
  cout << ans;
}
