package adv2017;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.InputMismatchException;

public class N616 {
	InputStream is;
	PrintWriter out;
	String INPUT = "";
	
	void solve()
	{
		int n = ni(), K = ni();
		int[] a = na(n);
		int mod = 1000000007;
		long ans = 0;
		for(int i = 0;i <= K;i++){
			ans += mahonianNumber(n, i, mod);
		}
		out.println(ans%mod);
	}
	
	public static long mahonianNumber(int n, int K, int mod)
	{
		int s = (int)Math.sqrt(2*(K+2));
		long[] pre = new long[K+1];
		long[] cur = new long[K+1];
		long[] sums = new long[K+1];
		pre[0] = 1;
		sums[0]++;
		for(int i = 1;i <= s;i++){
			for(int j = 0;j < i && j <= K;j++)cur[j] = 0;
			for(int j = i;j < K+1;j++){
				cur[j] = mod-pre[j-i] + cur[j-i];
				if(j-(n+1) >= 0)cur[j] += pre[j-(n+1)];
				while(cur[j] >= mod)cur[j] -= mod;
				sums[j] += cur[j];
			}
			long[] dum = pre; pre = cur; cur = dum;
		}
		int[] invs = enumInvs(K+2, mod);
		long ret = 0;
		
		long c = 1;
		long num = n%mod;
		for(int i = K;i >= 0;i--){
			ret += sums[i]%mod * c;
			ret %= mod;
			c = c * num % mod * invs[K-i+1] % mod;
			if(++num == mod)num = 0;
		}
		return ret;
	}	
	
	public static int[] enumInvs(int n, int mod) {
		int[] inv = new int[n + 1];
		inv[1] = 1;
		for (int i = 2; i <= n; i++) {
			inv[i] = (int) (inv[mod % i] * (long) (mod - mod / i) % mod);
		}
		return inv;
	}

	
	void run() throws Exception
	{
		is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes());
		out = new PrintWriter(System.out);
		
		long s = System.currentTimeMillis();
		solve();
		out.flush();
		if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms");
//		Thread t = new Thread(null, null, "~", Runtime.getRuntime().maxMemory()){
//			@Override
//			public void run() {
//				long s = System.currentTimeMillis();
//				solve();
//				out.flush();
//				if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms");
//			}
//		};
//		t.start();
//		t.join();
	}
	
	public static void main(String[] args) throws Exception { new N616().run(); }
	
	private byte[] inbuf = new byte[1024];
	public int lenbuf = 0, ptrbuf = 0;
	
	private int readByte()
	{
		if(lenbuf == -1)throw new InputMismatchException();
		if(ptrbuf >= lenbuf){
			ptrbuf = 0;
			try { lenbuf = is.read(inbuf); } catch (IOException e) { throw new InputMismatchException(); }
			if(lenbuf <= 0)return -1;
		}
		return inbuf[ptrbuf++];
	}
	
	private boolean isSpaceChar(int c) { return !(c >= 33 && c <= 126); }
	private int skip() { int b; while((b = readByte()) != -1 && isSpaceChar(b)); return b; }
	
	private double nd() { return Double.parseDouble(ns()); }
	private char nc() { return (char)skip(); }
	
	private String ns()
	{
		int b = skip();
		StringBuilder sb = new StringBuilder();
		while(!(isSpaceChar(b))){ // when nextLine, (isSpaceChar(b) && b != ' ')
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}
	
	private char[] ns(int n)
	{
		char[] buf = new char[n];
		int b = skip(), p = 0;
		while(p < n && !(isSpaceChar(b))){
			buf[p++] = (char)b;
			b = readByte();
		}
		return n == p ? buf : Arrays.copyOf(buf, p);
	}
	
	private int[] na(int n)
	{
		int[] a = new int[n];
		for(int i = 0;i < n;i++)a[i] = ni();
		return a;
	}
	
	private long[] nal(int n)
	{
		long[] a = new long[n];
		for(int i = 0;i < n;i++)a[i] = nl();
		return a;
	}
	
	private char[][] nm(int n, int m) {
		char[][] map = new char[n][];
		for(int i = 0;i < n;i++)map[i] = ns(m);
		return map;
	}
	
	private int[][] nmi(int n, int m) {
		int[][] map = new int[n][];
		for(int i = 0;i < n;i++)map[i] = na(m);
		return map;
	}
	
	private int ni() { return (int)nl(); }
	
	private long nl()
	{
		long num = 0;
		int b;
		boolean minus = false;
		while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
		if(b == '-'){
			minus = true;
			b = readByte();
		}
		
		while(true){
			if(b >= '0' && b <= '9'){
				num = num * 10 + (b - '0');
			}else{
				return minus ? -num : num;
			}
			b = readByte();
		}
	}
	
	private static void tr(Object... o) { System.out.println(Arrays.deepToString(o)); }
}