exercice

2+1+6-6+6-5-4+2=

4+5-4+3-2-6+6-5=

2+6-7+3-3-1+9-4=

2+6-7+3-3-1+9-4=

4-4+6+2-6-1+2+6=

7+1-2+3-3-6+3-2=

6-1+4-7-2+2+7-5=

6+1-7+6+2-1-6+5=

5+4-9+3+6-5-3+1=

4-4+7+1-1-6+1-2=