uses crt;
var n, a, b, c, d : longint;
begin
clrscr;
write('Nhap so : '); readln(n);
if (n >= 1111) and (n <= 9999) then
begin a := n div 1000;
b := (n - a * 1000) div 100;
c := (n - a * 1000 - b * 100) div 10;
d := n - a * 1000 - b * 100 - c * 10;
if (a = b) and (b = c) and (c = d) then
write(n,' la so tu quy') else write(n,' khong la so tu quy');
end else write(n,' khong la so tu quy');
readln
end.