Why ? My program looks ok ! Any trick or special test case ?

Thank you !

program de;
    var
    s:string;
    i,j,l,z,ost:integer;
    q:boolean;
    mas:array[1..20000] of char;
begin
   readln(s);
   l:=length(s);
   for i:=1 to l do
   mas[i]:=s[i];
   if l=1 then writeln(mas[i]) else
   if (l=2) and (mas[1]=mas[2]) then writeln(mas[1],'',mas[2])
   else
   begin
   q:=true;
   for i:=1 to l div 2 do
   if mas[i]<>mas[l-i+1] then q:=false;
   if q then
     begin
     for i:=1 to l do
     write(mas[i]);
     end
   else
   begin
   for i:=l div 2 to l do
   begin
   q:=true;
   z:=0;
   ost:=0;
   while z+i<>l do
   begin
   inc(z);
   if mas[i-z+1]<>mas[i+z] then q:=false;
   end;
   if q then ost:=1;
   z:=0;
   if q<>true then
   begin
   q:=true;
   while z+i<>l do
   begin
   inc(z);
   if mas[i-z]<>mas[i+z] then q:=false;
   end;
   end;
   if q then
    begin
     for j:=1 to i do
     write(mas[j]);
     if i<>l then i:=i+ost;
     for j:=i-1 downto 1 do
     write(mas[j]);
     break;
    end;
   end;
   end;
   end;
   readln;
end.

var S:string;
    i,j:integer;
    A,B:longint;
begin
     readln(s);
     A:=0;
     B:=0;
     j:=length(s) div 2;
     if odd(length(s)) then inc(j);
     for i:=1 to j do
     begin
        A:=A+Ord(s[i]);
     end;
     for i:=length(s) downto j do
     begin
        B:=B+Ord(s[i]);
     end;

     if a<>b then
     begin
      for i:=length(s)-1 downto 1 do
      begin
         s:=s+s[i];
      end;
      writeln(s);
     end else Writeln(s);
end.

I can't understand what's wrong with my code:

#include <iostream>
#include <string>
using namespace std;

bool isPalindrom(string str, unsigned n){
    unsigned num1=n, num2=str.size()-n-1, num;
    if(num1>num2) num=num2;
    else num=num1;
    for(unsigned a=0; a<=num; a++)
        if(str[n-a]!=str[n+a])
            return false;
    return true;
    }

int main(){
    string s1;
    unsigned x;
    cin>>s1;
    if(s1.size()==1){
        cout<<s1;
        return 0;
        }
    string str;
    for(unsigned a=s1.size()/2; a<s1.size(); a++)
    if(isPalindrom(s1, a)){
        x=a;
    for(unsigned a=0; a<x; a++)
        str+=s1[a];
    str+=s1[x];
    for(int b=x-1; b>=0; b--)
        str+=s1[b];
    if(s1 < str){
    cout<<str<<endl;
    return 0;
    }
    str.erase();
   }
    return 0;
    }

I cannot understand, why I have Memory Limit on test 22.
I have only 2 strings and 6 Longints.
Anybody help me!

I am getting WA with my bruteforce code. I can't understand why! Can some1 provide some cases?