MAYBE

Initial complexity problem:
1:	T:
		(?, 1)    f2(a, b, c) -> f2(a - 1, d, c) [ d >= 1 /\ a >= 2 ]
		(?, 1)    f2(a, b, c) -> f2(a - 1, d, c) [ 0 >= d + 1 /\ a >= 2 ]
		(?, 1)    f2(a, b, c) -> f1(a - 1, d, e) [ d >= 1 /\ 1 >= a ]
		(?, 1)    f2(a, b, c) -> f1(a - 1, d, e) [ 0 >= d + 1 /\ 1 >= a ]
		(?, 1)    f2(a, b, c) -> f2(a, 0, c) [ a >= 1 ]
		(?, 1)    f2(a, b, c) -> f1(a, 0, d) [ 0 >= a ]
		(1, 1)    f300(a, b, c) -> f2(a, b, c)
	start location:	f300
	leaf cost:	0

Repeatedly removing leaves of the complexity graph in problem 1 produces the following problem:
2:	T:
		(?, 1)    f2(a, b, c) -> f2(a - 1, d, c) [ d >= 1 /\ a >= 2 ]
		(?, 1)    f2(a, b, c) -> f2(a - 1, d, c) [ 0 >= d + 1 /\ a >= 2 ]
		(?, 1)    f2(a, b, c) -> f2(a, 0, c) [ a >= 1 ]
		(1, 1)    f300(a, b, c) -> f2(a, b, c)
	start location:	f300
	leaf cost:	3

A polynomial rank function with
	Pol(f2) = V_1 - 1
	Pol(f300) = V_1 - 1
orients all transitions weakly and the transitions
	f2(a, b, c) -> f2(a - 1, d, c) [ d >= 1 /\ a >= 2 ]
	f2(a, b, c) -> f2(a - 1, d, c) [ 0 >= d + 1 /\ a >= 2 ]
strictly and produces the following problem:
3:	T:
		(a + 1, 1)    f2(a, b, c) -> f2(a - 1, d, c) [ d >= 1 /\ a >= 2 ]
		(a + 1, 1)    f2(a, b, c) -> f2(a - 1, d, c) [ 0 >= d + 1 /\ a >= 2 ]
		(?, 1)        f2(a, b, c) -> f2(a, 0, c) [ a >= 1 ]
		(1, 1)        f300(a, b, c) -> f2(a, b, c)
	start location:	f300
	leaf cost:	3

Complexity upper bound ?

Time: 0.269 sec (SMT: 0.253 sec)