回帖：program year;
var y:integer;
begin
write('please enter the year!');
read(y);
if y mod 4=0 then do {then 后面不用加do }
begin
if y mod 100=0 then do {同上}
begin
if y mod 400=0 then do write('No!'); {同上，又else 前面不能有分号}
else write('Yes!');
end;
else write('No!');{同上一注释后半部分}
end;
else write('No!');{同上}
readln;
end.