YES(?, 2*a + 2*b + 3)

Initial complexity problem:
1:	T:
		(?, 1)    merge(a, b) -> merge(a - 1, b) [ a >= 1 /\ b >= 1 ]
		(?, 1)    merge(a, b) -> merge(a, b - 1) [ a >= 1 /\ b >= 1 ]
		(1, 1)    start(a, b) -> merge(a, b)
	start location:	start
	leaf cost:	0

A polynomial rank function with
	Pol(merge) = V_1 + V_2 - 1
	Pol(start) = V_1 + V_2 - 1
orients all transitions weakly and the transitions
	merge(a, b) -> merge(a, b - 1) [ a >= 1 /\ b >= 1 ]
	merge(a, b) -> merge(a - 1, b) [ a >= 1 /\ b >= 1 ]
strictly and produces the following problem:
2:	T:
		(a + b + 1, 1)    merge(a, b) -> merge(a - 1, b) [ a >= 1 /\ b >= 1 ]
		(a + b + 1, 1)    merge(a, b) -> merge(a, b - 1) [ a >= 1 /\ b >= 1 ]
		(1, 1)            start(a, b) -> merge(a, b)
	start location:	start
	leaf cost:	0

Complexity upper bound 2*a + 2*b + 3

Time: 0.127 sec (SMT: 0.122 sec)