Please give me a hand to deal with it!
3 array A[1:l], B[1:m],C[1:n], all sorted in
increasing order. for a integer 1<=k<=l+m+n, find an
algorithm to find the k-th smallest element in the
merge of A,B,C in O(logk) time. (assume that there's
no duplicate numbers in A,B,C)