YES(?, a + 2)

Initial complexity problem:
1:	T:
		(1, 1)    f1(a) -> f0(a)
		(?, 1)    f0(a) -> f0(a - 1) [ a >= 0 ]
	start location:	f1
	leaf cost:	0

A polynomial rank function with
	Pol(f1) = V_1 + 1
	Pol(f0) = V_1 + 1
orients all transitions weakly and the transition
	f0(a) -> f0(a - 1) [ a >= 0 ]
strictly and produces the following problem:
2:	T:
		(1, 1)        f1(a) -> f0(a)
		(a + 1, 1)    f0(a) -> f0(a - 1) [ a >= 0 ]
	start location:	f1
	leaf cost:	0

Complexity upper bound a + 2

Time: 0.064 sec (SMT: 0.062 sec)