#include <bits/stdc++.h>
using namespace std;
long long r, x, y, a, b, m, ans;
double mid;
int main() {
  cin >> r >> x >> y >> a >> b;
  r *= 2;
  m = (x - a) * (x - a) + (y - b) * (y - b);
  mid = sqrt(m);
  ans = mid / r;
  if (ans * r < mid) {
    ans++;
  }
  cout << ans;
  return 0;
}
