5 = 1 1 2 3 4 5 6 = 1 1 2 3 4 5 6 7 = 1 1 2 3 4 5 6 7 8 = 1
1*1+2-(3+4)+5=1*1+2+3-4+5-6=1*1*2*3*4-5*6+7=(1+1-2+3)-(4+5-6+7-8)=1