YES
0 QTRS
↳1 QTRSRRRProof (⇔, 18 ms)
↳2 QTRS
↳3 RisEmptyProof (⇔, 0 ms)
↳4 YES
a(a(x)) → b(b(b(x)))
b(b(x)) → c(c(c(x)))
c(c(x)) → d(d(d(x)))
b(x) → d(d(x))
c(d(d(x))) → a(x)
With this ordering the following rules can be removed by the rule removal processor [LPAR04] because they are oriented strictly:
POL(a(x1)) = 80 + x1
POL(b(x1)) = 53 + x1
POL(c(x1)) = 35 + x1
POL(d(x1)) = 23 + x1
a(a(x)) → b(b(b(x)))
b(b(x)) → c(c(c(x)))
c(c(x)) → d(d(d(x)))
b(x) → d(d(x))
c(d(d(x))) → a(x)