Program Maximum;
var
x1, x2, x3, x4, m: integer;
function max(a, b: integer): integer;
begin
if a > b
then max := a
else max := b
end;
begin
write('Введите 4 числа: ');
readln(x1, x2, x3, x4);
m := max(x1, max(x2, max(x3, x4)));
writeln('Максимальное: ', m);
end.