From physics:

X=V*Cos(A)*T
Y=V*Sin(A)*T-g*t^2/2

When ball is on the ground Y=0. So

0=V*Sin(A)*T-g*t^2/2  ==>   V*Sin(A)=G*t/2
==>  t=V*Sin(A)*2/G

X=V*Sin(A)*T = V*V*Sin(A)*Cos(A)*2/G

Sin(2A)=2Sin(A)*Cos(A), so:

X=V*V*Sin(2A)/G

Kinetic energy is m*V^2/2
It is decresead K times:

E1/E2=K

(M*V^2/2)/(M*V1^2/2)=k  ==>   V1=V/Sqrt(K)

So I wrote this program:

Var
 Sin2A,Len,V,K,T,X,A,Pii: Real;
begin
 Read(V,A,K);
 Len:=0;
 Pii:=3.1415926535;
 Sin2A:=Sin(A*Pii/90);
 Repeat
  X:=V*V*Sin2A/10;
  Len:=Len+X;
  V:=V/Sqrt(K);
 Until X<0.01;
 WriteLn(Len:0:2);
end.

It works good on test from example (5 15 2.50)
But it receivs [Wrong answer] :((

Help...

> Var
>  Sin2A,Len,V,K,T,X,A,Pii: Real;
> begin
>  Read(V,A,K);
>  Len:=0;
>  Pii:=3.1415926535;
>  Sin2A:=Sin(A*Pii/90);
>  Repeat
>   X:=V*V*Sin2A/10;
>   Len:=Len+X;
>   V:=V/Sqrt(K);
>  Until X<0.01;       => Write: "Until v<0.001". You'll got AC.
>  WriteLn(Len:0:2);
> end.

> > Var
> >  Sin2A,Len,V,K,T,X,A,Pii: Real;
> > begin
> >  Read(V,A,K);
> >  Len:=0;
> >  Pii:=3.1415926535;
> >  Sin2A:=Sin(A*Pii/90);
> >  Repeat
> >   X:=V*V*Sin2A/10;
> >   Len:=Len+X;
> >   V:=V/Sqrt(K);
> >  Until X<0.01;       => Write: "Until v<0.001". You'll got AC.
> >  WriteLn(Len:0:2);
> > end.
>
Thank You! ;)

u can use formula: len = sin(a) * cos(a) * sqr(v) * k / (k - 1) / 5;

> deaia

You must use eps more than 0,01(for example 1E-10)