def keypad_combinations(digits):
    if not digits:
        return[]
        mapping={
            '2':'ABC','3':'DEF','4':'GHI','5':'JKL','6':'MNO','7':'PQRS','8':'TUV','9':'WXYZ'}
            result=[]
            def backtrack(index,path):
                if index == len(digits):
                    result.append(path)
                    return
                for char in
                mapping.get(digits[index],''):
                    backtrack(index+1,path+char)
                    backtrack(0,"")
                    return result
                    Example usage
                    prit(keyopad_combinations("2 3"))