var n,i,k:integer;
Begin
write('nhap so nguyen to');read(n);
for i:=2 to n-1 do
if n mod i=0 then
begin
write('khong la so song to');
exit;
end;
while n>0 do
begin
k:=k+ n mod 10;
n:=n div 10;
end;
for i:=2 to k-1 do
if k mod i=0 then
begin
write('khong la so song to');
exit;
end;
write('co la so song to');
end.