Write a function: string solution (string &S, string &T); that, given two strings S and T consisting of N and M characters, respectively, determines whether string T can be obtained from string S by at most one simple operation from the set specified below. The function should return a string: "INSERT c" if string T can be obtained from string S by inserting a single character "c" at the beginning of the string; "REMOVE c" if string T can be obtained from string S by deleting a single character "c" from the end of the string; "SWAP c d" if string T can be obtained from string S by swapping two adjacent characters "c" and "d" (these characters should be distinct and in the same order as in string S; exactly one swap is performed); "EQUAL" if no operation is needed (strings T and S are equal); "IMPOSSIBLE" if none of the above works. Note that by characters "c" and "d" from the operations above, we mean any English alphabet lowercase letters. For example: given S = "gain" and T = "again", the function should return "INSERT a"; given S = "parks" and T = "park", the function should return "REMOVE s"; given S="form" and T = "from", the function should return "SWAP o r"; given S = "o" and T = "odd", the function should return "IMPOSSIBLE". Assume that: N and M are integers within the range [1..100]; string S consists only of lowercase letters (a-z); string T consists only of lowercase letters (a-z). In your solution, focus on correctness. The performance of your solution will not be the focus of the assessment.