uses crt;
var a, d, n : longint;
function element(a, d, n : longint) : longint;
begin
if n = 1 then element := a else
element := element(a + d, d, n - 1);
end;
begin
clrscr;
write('A -> ');
readln(a);
write('D -> ');
readln(d);
write('N -> ');
readln(n);
writeln('Answer = ', element(a, d, n));
readln;
end.