Edge Case - Contradiction

What if one customer wants $+1$ $+1$ and another wants $-1$ $-1$?

First clause $(x_1 lor x_1)$ gives: NOT $x_1 o x_1$. Second clause $(lnot x_1 lor lnot x_1)$ gives: $x_1 o$ NOT $x_1$. These $2$ edges form a cycle: $x_1 o$ NOT $x_1 o x_1$. The SCC contains both $x_1$ and NOT $x_1$. You can see the instance is unsatisfiable. Print IMPOSSIBLE. When a variable and its negation share an SCC, no valid assignment exists.