Xoa so trong so khac

uses crt;
var n:longint;
k,a,b,c,d,i,j:byte;
min,max:char;
st:string[10];
begin
clrscr;
repeat
write(`Nhap so N: `);
readln(n);
write(`Nhap so K: `);
readln(k);
if n>1000000000 then writeln(`Nhap lai so N nho hon 1000000000`);
if k>8 then writeln(`Nhap lai so K nho hon 9.`);
until (n<1000000000) and (k<9);
str(n,st); min:=st[1];
for i:=1 to k+1 do
if ord(st[i])>ord(max) then begin max:=st[i]; a:=i; end;
if a>1 then for i:=1 to a-1 do delete(st,i,1);
if (a-1)begin
for i:=1 to (k-a+1) do
begin
for j:=a+1 to length(st) do
if ord(st[j])delete(st,b,1);
end;
end;
write(` kq: `,st);
readln;
end.