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#include <iostream>
#include <vector>

constexpr long long mod = 1000 * 1000 * 1000 + 7;

std::vector<long long> get_combinations(int n, long long m) {
    std::vector<long long> result(n + 1, 0);
    result[2] = (m - 1) % mod;
    for (int i = 3; i <= n; ++i) {
        result[i] = (result[i - 1] * m) % mod;
    }
    return result;
}

std::vector<long long> get_powers(int n, long long m) {
    std::vector<long long> result(n + 1, 0);
    result[2] = m % mod;
    for (int i = 3; i <= n; ++i) {
        result[i] = (result[i - 1] * m) % mod;
    }
    return result;
}

long long solution() {
    long long n, m;
    std::cin >> n >> m;

    if (n < 2) return 0;

    std::vector<long long> combinations = get_combinations(n, m);
    std::vector<long long> powers = get_powers(n, m);

    std::vector<long long> dp(n + 1, 0);
    dp[2] = m % mod;
    
    if (n >= 3) {
        dp[3] = (m * m) % mod;
    }

    for (int i = 4; i <= n; ++i) {
        for (int j = i - 2; j >= 2; --j) {
            dp[i] += (dp[j] * combinations[i - j]) % mod;
            dp[i] = dp[i] % mod;
        }
        dp[i] += powers[i];
        dp[i] = dp[i] % mod;
    }

    return dp[n];
}

int main() {
    std::cout << solution() << "\n";
    return 0;
}