YES(?, 4*a + 6)

Initial complexity problem:
1:	T:
		(1, 1)    evaleasy2start(a) -> evaleasy2entryin(a)
		(?, 1)    evaleasy2entryin(a) -> evaleasy2bb1in(a)
		(?, 1)    evaleasy2bb1in(a) -> evaleasy2bbin(a) [ a >= 1 ]
		(?, 1)    evaleasy2bb1in(a) -> evaleasy2returnin(a) [ 0 >= a ]
		(?, 1)    evaleasy2bbin(a) -> evaleasy2bb1in(a - 1)
		(?, 1)    evaleasy2returnin(a) -> evaleasy2stop(a)
	start location:	evaleasy2start
	leaf cost:	0

Repeatedly removing leaves of the complexity graph in problem 1 produces the following problem:
2:	T:
		(1, 1)    evaleasy2start(a) -> evaleasy2entryin(a)
		(?, 1)    evaleasy2entryin(a) -> evaleasy2bb1in(a)
		(?, 1)    evaleasy2bb1in(a) -> evaleasy2bbin(a) [ a >= 1 ]
		(?, 1)    evaleasy2bbin(a) -> evaleasy2bb1in(a - 1)
	start location:	evaleasy2start
	leaf cost:	2

Repeatedly propagating knowledge in problem 2 produces the following problem:
3:	T:
		(1, 1)    evaleasy2start(a) -> evaleasy2entryin(a)
		(1, 1)    evaleasy2entryin(a) -> evaleasy2bb1in(a)
		(?, 1)    evaleasy2bb1in(a) -> evaleasy2bbin(a) [ a >= 1 ]
		(?, 1)    evaleasy2bbin(a) -> evaleasy2bb1in(a - 1)
	start location:	evaleasy2start
	leaf cost:	2

A polynomial rank function with
	Pol(evaleasy2start) = 2*V_1 + 1
	Pol(evaleasy2entryin) = 2*V_1 + 1
	Pol(evaleasy2bb1in) = 2*V_1 + 1
	Pol(evaleasy2bbin) = 2*V_1
orients all transitions weakly and the transition
	evaleasy2bb1in(a) -> evaleasy2bbin(a) [ a >= 1 ]
strictly and produces the following problem:
4:	T:
		(1, 1)          evaleasy2start(a) -> evaleasy2entryin(a)
		(1, 1)          evaleasy2entryin(a) -> evaleasy2bb1in(a)
		(2*a + 1, 1)    evaleasy2bb1in(a) -> evaleasy2bbin(a) [ a >= 1 ]
		(?, 1)          evaleasy2bbin(a) -> evaleasy2bb1in(a - 1)
	start location:	evaleasy2start
	leaf cost:	2

Repeatedly propagating knowledge in problem 4 produces the following problem:
5:	T:
		(1, 1)          evaleasy2start(a) -> evaleasy2entryin(a)
		(1, 1)          evaleasy2entryin(a) -> evaleasy2bb1in(a)
		(2*a + 1, 1)    evaleasy2bb1in(a) -> evaleasy2bbin(a) [ a >= 1 ]
		(2*a + 1, 1)    evaleasy2bbin(a) -> evaleasy2bb1in(a - 1)
	start location:	evaleasy2start
	leaf cost:	2

Complexity upper bound 4*a + 6

Time: 0.079 sec (SMT: 0.076 sec)