1 +2+3 +4+ 5 -6 -7+ 8- 9 =1
1+2+3+4+5-(6+7)+8-9=1
1+(2-3)-(4-5)+(6-7)-(8-9)=1-1+1-1+1=1
[(1+2+3+4)/5+6-7+8]/9=1