import java.io.*;

class Main {
	static StreamTokenizer in = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
	static double nextDouble() throws IOException {
		in.nextToken();
		return in.nval;
	}
	public static void main(String[] args) throws java.lang.Exception {
		double a, b;
		a = nextDouble();
		b = nextDouble();
		double t = (175*a - 75*b) / 100;
		double v = 75 / (a - t);
		double v0 = (50 - v*t) / t;
		System.out.printf("%.6f", v0);
	}
}