MAYBE

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

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

Complexity upper bound ?

Time: 0.220 sec (SMT: 0.205 sec)