import javax.swing.text.DateFormatter;
import java.io.*;
import java.io.IOException;
import java.io.InputStream;
import java.math.BigInteger;
import java.time.DateTimeException;
import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
import java.util.*;
import java.util.List;
import java.util.function.*;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import java.util.stream.Stream;

import static java.lang.Math.max;
import static java.lang.Math.min;
import static java.lang.Math.pow;
import static java.lang.Math.abs;

import static java.lang.String.format;


public class Main {
    final static int INF = Integer.MAX_VALUE>>1;
    final static int MOD = 1_000_000_007;
    final static int[] dx4 = { 0, 1, 0, -1 };
    final static int[] dy4 = { 1, 0, -1, 0 };
    final static int[] dx8 = {0, 1, 1,  1,  0, -1, -1, -1};
    final static int[] dy8 = {1, 1, 0, -1, -1, -1, 0, 1};
    public static void main(String[] args) {
        Scanner sc=new Scanner();
        int n = sc.nextInt();
        int k = sc.nextInt();
        int[] from = new int[n - 1];
        int[] to = new int[n - 1];
        for (int i = 0; i < n - 1; i++) {
            from[i]=sc.nextInt()-1;
            to[i] = sc.nextInt()-1;
        }
        Map<Integer,List<LGraph.Edge>> g=LGraph.makeLGraph(from,to);
        FactFactInv ffi=new FactFactInv(100100,MOD);

        Deque<Container> deq = new ArrayDeque<>();
        deq.add(new Container(-1,0));
        long ans=k;
        while (deq.size() > 0) {
            Container node=deq.removeFirst();
            List<Container> children = new ArrayList<>();
            for (LGraph.Edge edge : g.getOrDefault(node.node,new ArrayList<>())) {
                if(edge.to==node.parent)continue;
                children.add(new Container(node.node,edge.to));
            }
            if(children.size()==0)continue;
            int x=node.parent==-1?k-1:k-2;
            int y=children.size();
            if(x<y){
                put(0);
                return;
            }
            //put(node.node+"を見たとき子の並べ方は:"+(ffi.getFact(x)*ffi.getFactInv(x-y))%MOD+"通り");
            ans*=(ffi.getFact(x)*ffi.getFactInv(x-y))%MOD;
            ans%=MOD;
            for(Container c:children){
                deq.addFirst(c);
            }
        }
        put(ans%MOD);



    }
    static class Container{
        int parent;
        int node;

        public Container(int parent, int node) {
            this.parent = parent;
            this.node = node;
        }

        @Override
        public String toString() {
            return "Container{" +
                    "parent=" + parent +
                    ", node=" + node +
                    '}';
        }
    }

    final private static class FactFactInv{
        final long[] fact,factInv;
        final long mod;
        FactFactInv(int size,long mod){
            fact=new long[size+1];
            factInv=new long[size+1];
            this.mod=mod;
            init();
        }
        private void init(){
            fact[0]=1;
            for(int i=1;i<fact.length;i++){
                fact[i]=fact[i-1]*i%mod;
            }
            for(int i=0;i<factInv.length;i++){
                factInv[i]=ModPow.modPow(fact[i],mod-2,mod);
            }
        }
        long getFact(int index){
            return fact[index];
        }
        long getFactInv(int index){
            return factInv[index];
        }
        long getComb(int n,int r){
            return ((fact[n]*factInv[r])%mod*factInv[n-r])%mod;
        }
    }
    final static private class ModPow{
        //(x^y)%MOD
        public static long modPow(long x,long y,long mod){
            if(y==0)return 1;
            if(y%2==0){
                long halfY=y/2;
                long halfModPow = modPow(x,halfY,mod)%mod;
                return halfModPow*halfModPow%mod;
            }else{
                return x*modPow(x,y-1,mod)%mod;
            }
        }

    }
    final private static class LGraph{
        final public static class Edge{
            private int to,weight;
            protected Edge(int to, int weight) {
                this.to=to;
                this.weight=weight;
            }

            public int getTo() {
                return to;
            }

            public int getWeight() {
                return weight;
            }

            @Override
            public String toString() {
                return "Edge{" +
                        "to=" + to +
                        ", weight=" + weight +
                        '}';
            }
        }
        public static Map<Integer,List<Edge>> makeLGraph(int[] from,int[] to,int[] dist){
            if(from.length!=to.length||to.length!=dist.length){
                throw new IllegalArgumentException();
            }
            Map<Integer, List<Edge>> g = new HashMap<>();
            int m= from.length;
            for (int i = 0; i < m; i++) {
                List<Edge> list=g.getOrDefault(from[i],new ArrayList<>(1));
                list.add(new Edge(to[i],dist[i]));
                g.put(from[i],list);
                list = g.getOrDefault(to[i], new ArrayList<>(1));
                list.add(new Edge(from[i], -dist[i]));
                g.put(to[i],list);
            }
            return g;
        }
        public static Map<Integer,List<Edge>> makeLGraph(int[] from,int[] to){
            if(from.length!=to.length){
                throw new IllegalArgumentException();
            }
            int[] dist = new int[from.length];
            Arrays.fill(dist,0);
            return makeLGraph(from,to,dist);
        }
    }


    public static void print(Object object){
        System.out.print(object);
    }
    public static void put(Object object) {
        System.out.println(object);
    }
    public static void put(){
        System.out.println();
    }

    public static void printE(Object object){
        System.err.print("DEBUG:"+object);
    }
    public static void putE(Object object){
        System.err.println("DEBUG:"+object);
    }
    public static void putE(){
        System.err.println("DEBUG:");
    }

    public static void print(String format,Object... args){
        System.out.print(String.format(format,args));
    }
    public static void put(String format,Object... args) {
        System.out.println(String.format(format,args));
    }
    public static void printE(String format,Object... args){
        System.err.print("DEBUG:"+String.format(format,args));
    }
    public static void putE(String format,Object... args){
        System.err.println("DEBUG:"+String.format(format,args));
    }

    final static private class Scanner {
        private final InputStream in = System.in;
        private final byte[] buffer = new byte[1024];
        private int ptr = 0;
        private int buflen = 0;

        private boolean hasNextByte() {
            if (ptr < buflen) {
                return true;
            } else {
                ptr = 0;
                try {
                    buflen = in.read(buffer);
                } catch (IOException e) {
                    e.printStackTrace();
                }
                if (buflen <= 0) {
                    return false;
                }
            }
            return true;
        }

        private int readByte() {
            if (hasNextByte())
                return buffer[ptr++];
            else
                return -1;
        }

        private boolean isPrintableChar(int c) {
            return 33 <= c && c <= 126;
        }

        public boolean hasNext() {
            while (hasNextByte() && !isPrintableChar(buffer[ptr]))
                ptr++;
            return hasNextByte();
        }

        public String next() {
            if (!hasNext())
                throw new NoSuchElementException();
            StringBuilder sb = new StringBuilder();
            int b = readByte();
            while (isPrintableChar(b)) {
                sb.appendCodePoint(b);
                b = readByte();
            }
            return sb.toString();
        }

        public long nextLong() {
            if (!hasNext())
                throw new NoSuchElementException();
            long n = 0;
            boolean minus = false;
            int b = readByte();
            if (b == '-') {
                minus = true;
                b = readByte();
            }
            if (b < '0' || '9' < b) {
                throw new NumberFormatException();
            }
            while (true) {
                if ('0' <= b && b <= '9') {
                    n *= 10;
                    n += b - '0';
                } else if (b == -1 || !isPrintableChar(b)) {
                    return minus ? -n : n;
                } else {
                    throw new NumberFormatException();
                }
                b = readByte();
            }
        }

        public int nextInt() {
            long nl = nextLong();
            if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE)
                throw new NumberFormatException();
            return (int) nl;
        }

        public double nextDouble() {
            return Double.parseDouble(next());
        }
    }
    final static private class FixedIntPair {
        final public int x, y;
        final static public FixedIntPair ZEROS=new FixedIntPair(0,0);
        FixedIntPair(int x, int y) {
            this.x = x;
            this.y = y;
        }
        public static double distance(FixedIntPair fip1,FixedIntPair fip2){
            double x = (double) fip1.x - fip2.x;
            double y = (double) fip1.y - fip2.y;
            return Math.sqrt(x*x+y*y);
        }

        @Override
        public int hashCode() {
            return x+y;
        }

        @Override
        public boolean equals(Object obj) {
            if(obj==null)return false;
            if(!(obj instanceof FixedIntPair)) return false;
            FixedIntPair pair=(FixedIntPair) obj;
            return this.x==pair.x&&this.y==pair.y;
        }

        @Override
        public String toString() {
            return String.format(FixedIntPair.class.getSimpleName()+":(%d,%d)", x, y);
        }
    }
    final static private class FixedLongPair {
        final public long x, y;
        final static public FixedLongPair ZEROS=new FixedLongPair(0,0);
        FixedLongPair(long x, long y) {
            this.x = x;
            this.y = y;
        }
        public static double distance(FixedLongPair flp1,FixedLongPair flp2){
            double x = (double) flp1.x - flp2.x;
            double y = (double) flp1.y - flp2.y;
            return Math.sqrt(x*x+y*y);
        }

        @Override
        public int hashCode() {
            return (int)x+(int)y;
        }

        @Override
        public boolean equals(Object obj) {
            if(obj==null)return false;
            if(!(obj instanceof FixedLongPair)) return false;
            FixedLongPair pair=(FixedLongPair)obj;
            return this.x==pair.x&&this.y==pair.y;
        }

        @Override
        public String toString() {
            return String.format(FixedLongPair.class.getSimpleName()+":(%d,%d)", x, y);
        }
    }
    final static private class Binary{
        public static String toZeroPadding(int i){
            return String.format("%"+Integer.toBinaryString(-1).length()+"s",Integer.toBinaryString(i)).replace(' ','0');
        }
        public static String toZeroPadding(long i){
            return String.format("%"+Long.toBinaryString(-1).length()+"s",Long.toBinaryString(i)).replace(' ','0');
        }
    }

    final static private class Util {
        static long gcd(long a,long b){
            a=Math.abs(a);
            b=Math.abs(b);
            if(a<b){
                long tmp=a;
                a=b;
                b=tmp;
            }
            while(b!=0){
                long r=a%b;
                a=b;
                b=r;
            }
            return a;
        }
        static int gcd(int a,int b){
            a=Math.abs(a);
            b=Math.abs(b);
            if(a<b){
                int tmp=a;
                a=b;
                b=tmp;
            }
            while(b!=0){
                int r=a%b;
                a=b;
                b=r;
            }
            return a;
        }
        static long lcm(long a,long b){
            long gcd=gcd(a,b);
            long result=b/gcd;
            return a*result;
        }
        static boolean isValidCell(int i,int j,int h,int w){
            return i>=0&&i<h&&j>=0&&j<w;
        }
    }
}































































/*
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