var
   k, l, t, v, a: extended;

const
     pi = 3.1415926535;

begin
     readln(v, a, k);
     l := sqr(v) * sin(a * pi / 90) / 10;
     k := 1 / k;
     t := 1;
     while l * t >= 0.001 do t := t * k;
     l := l * (t - 1) / (k - 1);
     writeln(l: 0: 2);
end.