PLEASE HELP WITH C++

Suppose A, B, C are arrays of integers of size M, N, and M+N respectively. The numbers in array A appear in ascending order while the numbers in array B appear in descending order. Write a user defined function in C++ to produce third array C by merging arrays A and B in ascending order. Use A, B, and C as arguments in the function. You will need to ask user to input M and N, and based on those inputs user needs to fill the arrays A and B in an appropriate order. If user wants to input wrong order of values, your program should not accept it, and should ask for appropriate value.