Given a string as input. When `M` is hit program would copy the preceding character at the end of the string and then remove itself and when `N` is hit program will remove the next character of the string and remove itself too

AlgorithmicString.py

def MandN(string):
    result = ""
    string_iter = iter(string)
    for i in string_iter:
        if (i == "M"):
            if (len(result) != 0):
                result += result[-1]
        elif (i == "N"):
            try:
                next(string_iter)
            except:
                continue
        else:
            result += i
    return result
    
print(MandN("aNxMrgMM"))