999*7778+3333*666 =999*7778+3*1111*333*2 = 999*7778+999*2222 = 999*(7778+2222=999*10000=9990000
999*7778+3333*666=333*(3*7778+6666)=333*3*(7778+2222)=999*10000=9990000 .
