#include <bits/stdc++.h>
using namespace std;

ifstream in ( "colorare3.in"  );
ofstream out( "colorare3.out" );

const int DIM = 1e5 + 5;
const int MOD = 1e9 + 7;

int cnt[DIM];

int main( void ) {
    
    int n, k;
    in >> n >> k;
    
    for( int i = 1; i < n; i ++ ) {
        int x, y;
        in >> x >> y;
        
        cnt[x] ++; cnt[y] ++;
    }
    
    int ans = k;
    for( int i = 1; i <= n; i ++ )
    for( int j = k - cnt[i] + 1; j < k; j ++ )
        ans = ( 1LL * ans * j ) % MOD;
    
    out << ans << endl;
    return 0;
}