a and b
YES! i=1
a and c
YES! i=2
a and a
fail.
b and c
YES! i=2
b and a
YES! i=3
b and b
YES! i=4
b and a
fail.
c and a
YES! i=3
c and b
YES! i=4
c and a
fail.
a and b
YES! i=4
a and a
YES! i=5
a and a
fail.
b and a
YES! i=5
b and a
fail.
a and a
YES! i=6
a and c
YES! i=7
a and b
YES! i=8
a and c
fail.
a and c
YES! i=7
a and b
YES! i=8
a and c
fail.
c and b
YES! i=8
c and c
YES! i=9
c and  
fail.
b and c
YES! i=9
b and  
fail.
c and  
fail.
586