function nto(n:longint):boolean;
var i:longint;
begin
if n < 2 then exit(false);
 for i := 2 to trunc(sqrt(n)) do
  if n mod i = 0 then exit(false);
 exit(true);
end;
var n,st:string;
    i,k,m:longint;
begin
write('Nhap so n:');readln(n);
write('Nhap so k: ');readln(k);
st:='';
if (k>=length(n)) then
   begin
      writeln('a) Ket qua sau khi xoa la:0');
      writeln('b) So n co ',length(n),' chu so');
      writeln('c) KHONG THE');
      readln;
      exit;
   end;
for i := 1 to length(n)-k do
st := st + n[i];
val(st,m);
while (m <> 0) and (nto(m)=false) do m := m div 10;
writeln('a) Ket qua sau khi xoa la:',st);
writeln('b) So n co ',length(n),' chu so');
if m = 0 then writeln('c) KHONG THE')
 else writeln('c) Xoa duoc:',m);
readln;
end.