#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import itertools

def main():
    n, b = map(int, input().split(' '))
    input_list = list(map(int, input().split(' ')))
    result = 0
    pattern_list = list(itertools.permutations(input_list, n))
    for a_list in pattern_list:
        max_score = -1
        count = 0
        for each in a_list:
            if max_score < each:
                max_score = each
                count += 1
        result += (count * (b ** count))
    print(result % (10 ** 9 + 7))



if __name__ == '__main__':
    import sys
    sys.exit(main())