All right!I think.
PROGRAM Ural1114;
Var
   S:Extended;
   I,J,K,P,Q,N,A,B:Byte;
   F:Array[1..20,0..15,0..15] Of Extended;
Begin
     ReadLN(N,A,B);
     FillChar(F,SizeOf(F),0);
     For I:=0 To A Do
         For J:=0 To B Do F[1,I,J]:=1;
     For I:=2 To N Do
         For J:=0 To A Do
             For K:=0 To B Do
             Begin
                  For P:=0 To J Do
                      For Q:=0 To K Do F[I,J,K]:=F[I,J,K]+F[I-1,P,Q];
             End;
     S:=0;
     For I:=0 To A Do
         For J:=0 To B Do
             S:=S+F[N,I,J];
     WriteLn(S:0:0);
End.

> All right!I think.
> PROGRAM Ural1114;
> Var
>    S:Extended;
>    I,J,K,P,Q,N,A,B:Byte;
>    F:Array[1..20,0..15,0..15] Of Extended;
> Begin
>      ReadLN(N,A,B);
>      FillChar(F,SizeOf(F),0);
>      For I:=0 To A Do
>          For J:=0 To B Do F[1,I,J]:=1;
>      For I:=2 To N Do
>          For J:=0 To A Do
>              For K:=0 To B Do
>              Begin
>                   For P:=0 To J Do
>                       For Q:=0 To K Do F[I,J,K]:=F[I,J,K]+F[I-
1,P,Q];
>              End;
>      S:=0;
>      For I:=0 To A Do
>          For J:=0 To B Do
>              S:=S+F[N,I,J];
>      WriteLn(S:0:0);
> End.