#include <bits/stdc++.h>
using namespace std;
int x, y, w, z;
long long sol;
double length, r;
int main() {
  cin.sync_with_stdio(false);
  cin >> r >> x >> y >> w >> z;
  length = sqrt(1LL * abs(x - w) * abs(x - w) + 1LL * abs(y - z) * abs(y - z));
  r *= 2;
  sol = length / r;
  length -= 1.0 * sol * r;
  if (length > 0) sol++;
  cout << sol << "\n";
  return 0;
}
