5
1 1
X1
1 1
~X1
3 5
X1 v X2 v X3
X1 v ~X2
X2 v ~X3
X3 v ~X1
~X1 v ~X2 v ~X3
1 2
X1
~X1
4 4
X1 v ~X2 v X3
~X1 v X3
~X3
X2 v X3
