That's my source, it's only 125000 operation maximum, but is got MLE#8, WHY ???????????

var a,t,ta,tt:string;
    n,i,ans:longint;

begin
readln(n);
ans:=-1;
readln(a);
readln(t);
ta:=a;tt:=t;

for i:=1 to (n div 2+1) do
    begin
    if a<>t then
       begin
       a:=a+a[1];delete(a,1,1);
       end else
           begin
           ans:=n-i+1;
           break;
           end;

    if ta<>tt then
       begin
       tt:=tt+tt[1];delete(tt,1,1);
       end else
           begin
           ans:=i-1;
           break;
           end;

    end;

writeln(ans mod n);
end.