请问字符串SHL左移后怎么还原?

Function   SHLStr(Str1:String):String;
var
    a:LongWord;
    Int1,Int2:Integer;
    j,j1:Integer;
    sum:LongWord;
begin
        Int2:=Length(Str1);
        for   j1:=1   to   Int2   do
            begin
                a:=ord(Str1[j1]) shl   7;
                sum:=sum+a;
            end;
        Result:=IntToStr(sum);
end;怎样写出还原函数呢?
SHLStr('你好'); => 4381616