Integer concatenation

Concatenation of two integers is obtained as follows: First, convert both integers to strings. Then concatenate both strings into one and convert this concatenated string back to integer. For example, concatenation of $6$ and $7$ is $CONC(6, 7) = 67$, concatenation of $123$ and $45$ is $CONC(123, 45) = 12345$. You are given an array $A$ consisting of $N$ integers. You are also given two integers