n = 1223356789
chuso = str(n)
bacthang = False
if len(chuso) > 1:
    bacthang = True
    i=0
    while bacthang and (i < len(chuso)-1):
        if int(chuso[i]) > int(chuso[i+1]):
            bacthang = False
        else:
            i += 1
if bacthang:
    print('Day la so bac thang')
else:
    print('Day khong la so bac thang')