pascal读入一个字串，（长度不大于50）删出字符串中相同的字符。

var
s:string;
a:array [1..50] of char;
i,j,k:integer;
fl:boolean;
begin
readln(s);
k:=1;
for i:=1 to length(s) do
begin
fl:=true;
for j:=1 to i do
if (i<>j) and (s[i]=s[j]) then fl:=false;
if fl=true then begin a[k]:=s[i]; inc(k); end;
end;
for i:=1 to k do
write(a[i]);
readln;
end.