1-2+(3+45)/6=7,(1+2+34+5)/6=7
1+2+34-5*6=7,1/2+(34+5)/6=7
(1+23)/4-5+6=7,(12-3-4)/5+6=7
12/(3+4+5)+6=7,12/3+4+5-6=7
1+2-3-4+5+6=7,1+2/(3+4-5)*6=7
1-2+3+4-5+6=7,(1-2+3)*4+5-6=7
1-(2-3-4)/5*6=7,1-2*(3-4-5)-6=7
1-2*3*4+5*6=7,1-2/(3-4*5/6)=7
(1*2-3)*4+5+6=7,1*(2-3)*4+5+6=7
1*2/(3+4-5)+6=7,1/(2+3)+4/5+6=7
1/(2-3)*4+5+6=7,1/2*(3+4-5)+6=7
1/2*3*4-5+6=7,(1/2/3-4+5)*6=7
排除中间过程有负数的,共有18个算式：
1-2+(3+45)/6=7,(1+2+34+5)/6=7
1+2+34-5*6=7,1/2+(34+5)/6=7
(1+23)/4-5+6=7,(12-3-4)/5+6=7
12/(3+4+5)+6=7,12/3+4+5-6=7
1+2-3-4+5+6=7,1+2/(3+4-5)*6=7
1-2+3+4-5+6=7,(1-2+3)*4+5-6=7
1-2*3*4+5*6=7,1*2/(3+4-5)+6=7
1/(2+3)+4/5+6=7,1/2*(3+4-5)+6=7
1/2*3*4-5+6=7,(1/2/3-4+5)*6=7
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