# include <cstdio>

const char FIN[] = "colorare3.in", FOU[] = "colorare3.out";
const int MOD = 1000000007;
const int MAX = 100007;

int N, K, sol = 1 ;
int V[MAX];

int main()
{
    freopen ( FIN, "r", stdin ) ;
    freopen ( FOU, "w", stdout ) ;

    scanf ( "%d %d", &N, &K ) ;

    for (int i = 1, A = 0, B = 0; i < N; ++i)
        scanf ( "%d %d", &A, &B ) , ++V[ A ], ++V[ B ] ;

    sol = K ;

    for (int i = 1; i <= N; ++i)
        for (int j = 1; j < V[i]; ++j)
            sol = ( long long ) sol * ( K - j ) % MOD;

    printf ( "%d", sol ) ;

    return 0;
}