//1
var
y, a, b, c, d : real;
begin
readln(a, b, c, d);
y := (a/c) * (b/d) - ((a*b-c)/(c*d));
writeln(y);
end.
//2
uses math;
var
f, a, s : real;
begin
readln(a, s);
f := power(s, 2) + (a / (a+s)) * sqrt(power(s, 2) - s) - 176;
writeln(f);
end.
//3
uses math;
var
z, x, y : real;
begin
readln(x, y);
z := sqrt(abs(x-1) + y) / (1 + power(x, 2));
writeln(z);
end.
