uses crt;
procedure pr(var a:integer;p:integer;n:integer;var sum:integer);
begin
if n = 1 then sum:=a
else
begin
pr(a,p,n-1,sum);
a:=a+p;
sum:=sum+a;
end;
end;
var s,a,p:integer;
n:integer;
begin
clrscr;
write('Vvedite A0 : ');readln(a);
write('Vvedite p : ');readln(p);
write('Vvedite n : ');readln(n);
pr(a,p,n,s);
writeln('Sum = ',s);
readln
end.