Given an array of strings below, write a C++ program to concatenate only those strings which start with 'a' or 'A' and print the string formed in output. Given array:  string St[5] = {"Hello","Program", "algorithm","Approval","Language"}

Process or set of rules that allow for the solving of specific, well-defined computational problems through a specific series of commands. This topic is fundamental in computer science, especially with regard to artificial intelligence, databases, graphics, networking, operating systems, and security.