whats wrong?

program fly;
const okn='window';
      ser='neither';
      proh='aisle';
var i,r,n,bb:integer;
    s,s1:string;
    m:char;
begin
readln(s);
n:=length(s);
m:=s[n];
s1:=s;
delete(s1,n,1);
val(s1,r,bb);
if r<3 then
 if (m='A') or (m='D') then writeln(okn) else writeln(proh) else
if r<21 then
 if (m='A') or (m='F') then writeln(okn) else writeln(proh) else
if r<65 then
if (m='A') or (m='K') then writeln(okn) else
if (m='C') or (m='D') or (m='G') or (m='H') then writeln(proh) else writeln(ser);
end.