第三个点

10 + (1 -a) +(a +8)-(9-8)
10
9+9+9+8+9+1-9-5-1-(8-8)
9999 + 9999+9999+9999-(9999 + 9999+9999+9999)+6+ 5
1-13
  6                                    
((6 +1)-6-a-8-( 1-(a +8))-(9999   -9990)- 3
6+9+8+5+9+2+4+1+8+3+9+3+a+3+8+7 -8-6+8+9+4+1+1+7+6
1-1-1-1-1-1-1-1-1-1-1-1-1-1  
12
10+8
8+10

((6 +1)-6-a-8-( 1-(a +8))-(9999 -9990)- 3括号不匹配吧