var x1;
var x2;
var x3;

f1:  x1 >= 0 complements
	x1 + 2*x2 + 3*x3 >= 1;

f2:  x2 >= 0 complements
	x2 - x3 >= -1;

f3:  x3 >= 0 complements
	x1 + x2 >= -1;