Problem: Vasya has recently bought some land and decided to surround it with a wooden fence.

He went to a company called "Wooden board" that produces wooden boards for fences. Vasya read in the catalog of products that the company has at its disposal n different types of wood. The company uses the i-th type of wood to produce a board of this type that is a rectangular ai by bi block.

Vasya decided to order boards in this company and build a fence from them. It turned out that the storehouse of the company is so large that Vasya can order arbitrary number of boards of every type. Note that Vasya is allowed to turn the boards as he builds the fence. However, Vasya cannot turn square boards.

Vasya is required to construct a fence of length l, however, an arbitrary fence won't do. Vasya wants his fence to look beautiful. We'll say that a fence is beautiful if and only if the following two conditions are fulfilled:

  * there are no two successive boards of the same type 
  * the first board of the fence has an arbitrary length, and the length of each subsequent board equals the width of the previous one 



In other words, the fence is considered beautiful, if the type of the i-th board in the fence is different from the i - 1-th board's type; besides, the i-th board's length is equal to the i - 1-th board's width (for all i, starting from 2).

Now Vasya wonders, how many variants of arranging a fence for his land exist. Your task is to count the number of different beautiful fences of length l.

Two fences will be considered the same if the corresponding sequences of fence boards types and rotations are the same, otherwise the fences are different. Since the sought number can be large enough, you need to calculate the answer modulo 1000000007 (109 + 7).

Input

The first line contains two integers n and l (1 ≤ n ≤ 100, 1 ≤ l ≤ 3000) — the number of different board types and the fence length, correspondingly. Next n lines contain descriptions of board types: the i-th line contains two integers ai and bi (1 ≤ ai, bi ≤ 100) — the sizes of the board of the i-th type. All numbers on the lines are separated by spaces.

Output

Print a single integer — the sought number of variants modulo 1000000007 (109 + 7).

Examples

Input

2 3
1 2
2 3


Output

2


Input

1 2
2 2


Output

1


Input

6 6
2 1
3 2
2 5
3 3
5 1
2 1


Output

20

Note

In the first sample there are exactly two variants of arranging a beautiful fence of length 3: 

  * As the first fence board use the board of the first type of length 1 and width 2. As the second board use board of the second type of length 2 and width 3. 
  * Use one board of the second type after you turn it. That makes its length equal 3, and width — 2. 

Solution (in JAVA):

Solution:
import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.StringTokenizer;
 
public class Main {
	static PrintWriter out = new PrintWriter(System.out, true);
 
	static int n, L;
	static Pair a[];
	static final long MOD = 1000000007;
	static long memo[][][];
	static boolean v[][][];
 
	static long solve(int last, int l, int rotated) {
		if (l == L) {
			return 1;
		}
		if (l > L) {
			return 0;
		}
		if (v[last][l][rotated]) {
			return memo[last][l][rotated];
		}
		v[last][l][rotated] = true;
		int prevW = a[last].y;
		if (rotated == 1) {
			prevW = a[last].x;
		}
		long sum = 0;
		for (int i = 0; i < n; i++) {
			if (i == last)
				continue;
			if (prevW == a[i].x) {
				sum += solve(i, l + a[i].x, 0);
				sum %= MOD;
			}
			if (prevW == a[i].y && a[i].x != a[i].y) {
				sum += solve(i, l + a[i].y, 1);
				sum %= MOD;
			}
		}
		return memo[last][l][rotated] = sum % MOD;
	}
 
	public static void main(String[] args) throws IOException {
		FastReader input = new FastReader();
		n = input.nextInt();
		L = input.nextInt();
		a = new Pair[n];
 
		for (int i = 0; i < n; i++) {
			int x = input.nextInt();
			int y = input.nextInt();
			a[i] = new Pair(x, y);
		}
		long sum = 0;
		memo = new long[n + 1][L + 1][2];
		v = new boolean[n + 1][L + 1][2];
		for (int i = 0; i < n; i++) {
			sum += solve(i, a[i].x, 0);
			if (a[i].x != a[i].y)
				sum += solve(i, a[i].y, 1);
			sum %= MOD;
		}
		out.println((MOD + sum) % MOD);
		out.flush();
	}
 
	static class FastReader {
		BufferedReader br;
		StringTokenizer st;
 
		public FastReader() {
			// try {
			// br = new BufferedReader(new FileReader(new File("scoreboard.in")));
			// } catch (FileNotFoundException e) {
			// e.printStackTrace();
			// }
			br = new BufferedReader(new InputStreamReader(System.in));
		}
 
		String next() throws IOException {
			while (st == null || !st.hasMoreElements()) { st = new StringTokenizer(br.readLine()); }
			return st.nextToken();
		}
 
		int nextInt() throws NumberFormatException, IOException { return Integer.parseInt(next()); }
 
		long nextLong() throws NumberFormatException, IOException { return Long.parseLong(next()); }
 
		double nextDouble() throws NumberFormatException, IOException { return Double.parseDouble(next()); }
 
		String nextLine() throws IOException {
			String str = "";
			str = br.readLine();
			return str;
		}
 
		boolean hasNext() throws IOException { return br.ready(); }
	}
 
	static class con {
		static int IINF = (int) 1e9;
		static int _IINF = (int) -1e9;
		static long LINF = (long) 1e15;
		static long _LINF = (long) -1e15;
		static double EPS = 1e-9;
	}
 
	static class Triple implements Comparable<Triple> {
		int x;
		int y;
 
		int z;
 
		Triple(int x, int y, int z) {
			this.x = x;
			this.y = y;
			this.z = z;
		}
 
		@Override
		public int compareTo(Triple o) {
			if (x == o.x && y == o.y)
				return z - o.z;
			if (x == o.x)
				return y - o.y;
			return x - o.x;
		}
 
		@Override
		public String toString() { return "(" + x + ", " + y + ", " + z + ")"; }
	}
 
	static class Pair implements Comparable<Pair> {
		int x;
		int y;
 
		Pair(int x, int y) {
			this.x = x;
			this.y = y;
 
		}
 
		@Override
		public int compareTo(Pair o) {
			if (x == o.x)
				return y - o.y;
			return x - o.x;
		}
 
		@Override
		public String toString() {
 
			return "(" + x + ", " + y + ")";
		}
 
	}
 
	static void shuffle(long[] a) {
		for (int i = 0; i < a.length; i++) {
			int r = i + (int) (Math.random() * (a.length - i));
			long tmp = a[r];
			a[r] = a[i];
			a[i] = tmp;
		}
	}
 
	static int gcd(int a, int b) { return b == 0 ? a : gcd(b, a % b); }
 
	static class DSU {
 
		int[] p, rank, setSize;
		int numSets;
 
		DSU(int n) {
			p = new int[n];
			rank = new int[n];
			setSize = new int[n];
			numSets = n;
 
			for (int i = 0; i < n; i++) {
				p[i] = i;
				setSize[i] = 1;
			}
 
		}
 
		int findSet(int n) { return p[n] = p[n] == n ? n : findSet(p[n]); }
 
		boolean isSameSet(int n, int m) { return findSet(n) == findSet(m); }
 
		void mergeSet(int n, int m) {
 
			if (!isSameSet(n, m)) {
				numSets--;
				int p1 = findSet(n);
				int p2 = findSet(m);
 
				if (rank[p1] > rank[p2]) {
					p[p2] = p1;
					setSize[p1] += setSize[p2];
				} else {
					p[p1] = p2;
					setSize[p2] += setSize[p1];
					if (rank[p1] == rank[p2])
						rank[p1]++;
				}
			}
 
		}
 
		int size() { return numSets; }
 
		int setSize(int n) { return setSize[findSet(n)]; }
 
	}
 
	static class Reader {
		final private int BUFFER_SIZE = 1 << 16;
		private DataInputStream din;
		private byte[] buffer;
		private int bufferPointer, bytesRead;
 
		public Reader() {
			din = new DataInputStream(System.in);
			buffer = new byte[BUFFER_SIZE];
			bufferPointer = bytesRead = 0;
		}
 
		public Reader(String file_name) throws IOException {
			din = new DataInputStream(new FileInputStream(file_name));
			buffer = new byte[BUFFER_SIZE];
			bufferPointer = bytesRead = 0;
		}
 
		public String readLine() throws IOException {
			byte[] buf = new byte[1024];
			int cnt = 0, c;
			while ((c = read()) != -1) {
				if (c == '\n')
					break;
				buf[cnt++] = (byte) c;
			}
			return new String(buf, 0, cnt);
		}
 
		public int nextInt() throws IOException {
			int ret = 0;
			byte c = read();
			while (c <= ' ')
				c = read();
			boolean neg = (c == '-');
			if (neg)
				c = read();
			do { ret = ret * 10 + c - '0'; } while ((c = read()) >= '0' && c <= '9');
			if (neg)
				return -ret;
			return ret;
		}
 
		public long nextLong() throws IOException {
			long ret = 0;
			byte c = read();
			while (c <= ' ')
				c = read();
			boolean neg = (c == '-');
			if (neg)
				c = read();
			do { ret = ret * 10 + c - '0'; } while ((c = read()) >= '0' && c <= '9');
			if (neg)
				return -ret;
			return ret;
		}
 
		public double nextDouble() throws IOException {
			double ret = 0, div = 1;
			byte c = read();
			while (c <= ' ')
				c = read();
			boolean neg = (c == '-');
			if (neg)
				c = read();
			do { ret = ret * 10 + c - '0'; } while ((c = read()) >= '0' && c <= '9');
			if (c == '.')
				while ((c = read()) >= '0' && c <= '9')
					ret += (c - '0') / (div *= 10);
			if (neg)
				return -ret;
			return ret;
		}
 
		private void fillBuffer() throws IOException {
			bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE);
			if (bytesRead == -1)
				buffer[0] = -1;
		}
 
		private byte read() throws IOException {
			if (bufferPointer == bytesRead)
				fillBuffer();
			return buffer[bufferPointer++];
		}
 
		public void close() throws IOException {
			if (din == null)
				return;
			din.close();
		}
	}
 
}