如题，高手出来教教小弟一个低级问题，就是如何判断一个数是不是回文数。详细点，谢谢

var s:ansistring;
var i:longword=1;
var b:boolean=true;
begin
readln(s);
repeat
i:=i+1;
b:=b and (s[i]=s[length(s)-i+1]);
until (i>length(s) div 2) or not(b);
writeln(b);
end.

function check(s:string):boolean;
var i:longint;
begin
for i:=1 to ord(s[0]) do if s[i]<>s[ord(s[0])-i+1] then exit(false)
exit(true);
end;
var s:string;
begin
readln(s);
if check(s) then writeln('yes') else writeln('no');
end.