#include <bits/stdc++.h>
using namespace std;
using ll = long long;
struct custom_hash {
  static uint64_t splitmix64(uint64_t x) {
    x += 0x9e3779b97f4a7c15;
    x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
    x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
    return x ^ (x >> 31);
  }
  size_t operator()(uint64_t x) const {
    static const uint64_t FIXED_RANDOM =
        chrono::steady_clock::now().time_since_epoch().count();
    return splitmix64(x + FIXED_RANDOM);
  }
};
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long double r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  long double dis = ceil(sqrtl(pow(abs(x1 - x), 2) + pow(abs(y1 - y), 2)));
  long double res = ceil(dis / (2 * r));
  cout << std::fixed << std::setprecision(0) << res << "\n";
}
