|A TriFibonacci sequence begins by defining the first three elements A, A and A. The remaining elements are calculated using the following recurrence:|
A[i] = A[i-1] + A[i-2] + A[i-3]
You are given a int A which contains exactly one element that is equal to -1, you must replace this element with a positive number in a way that the sequence becomes a TriFibonacci sequence. Return this number. If no such positive number exists, return -1.
|-||The constraints for the elements of the input int A do not necessarily apply for the replacement to the missing element.|
|-||A will contain between 4 and 20 elements, inclusive.|
|-||Each element of A will be -1 or between 1 and 1000000, inclusive.|
|-||Exactly one element of A will be -1.|