public static void solve(Input in, PrintWriter out) throws IOException {
        double xa = in.nextDouble();
        double ya = in.nextDouble();
        double xb = in.nextDouble();
        double yb = in.nextDouble();
        double ra = Math.sqrt(xa * xa + ya * ya);
        double rb = Math.sqrt(xb * xb + yb * yb);
        double alpha = Math.atan2(Math.abs(xa * yb - xb * ya), xa * xb + ya * yb);
        double ans = Math.abs(ra - rb) + Math.min(ra, rb) * alpha;
        ans = Math.min(ans, ra + rb);
        out.println(ans);
    }