#include <bits/stdc++.h>
using namespace std;
int n, l;
int a[101][2];
long long F[101][3001][2];
long long ans = 0;
long long dp(int i, int len, int j) {
  if (len <= 0) return 0;
  if (F[i][len][j] != -1) {
    return F[i][len][j];
  }
  long long ans = 0;
  for (int ij = 0; ij <= 1; ij++) {
    for (int ii = 1; ii <= i - 1; ii++)
      if (a[i][j] == a[ii][(!ij)]) {
        if (ij == 1 && a[ii][1] == a[ii][0]) continue;
        ans += dp(ii, len - a[i][j], ij);
        ans %= 1000000007;
      }
    for (int ii = i + 1; ii <= n; ii++)
      if (a[i][j] == a[ii][(!ij)]) {
        if (ij == 1 && a[ii][1] == a[ii][0]) continue;
        ans += dp(ii, len - a[i][j], ij);
        ans %= 1000000007;
      }
  }
  return F[i][len][j] = ans;
}
int main() {
  ios_base ::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  clock_t start = clock();
  cin >> n >> l;
  for (int i = 1; i <= n; i++)
    for (int j = 0; j <= 1; j++) {
      for (int k = 1; k <= l; k++) F[i][k][j] = -1;
      cin >> a[i][j];
      F[i][a[i][j]][j] = 1;
    }
  for (int i = 1; i <= n; i++)
    for (int j = 0; j <= 1; j++) {
      if (j == 1 && a[i][0] == a[i][1]) continue;
      ans += dp(i, l, j);
      ans %= 1000000007;
    }
  cout << ans << '\n';
  cerr << "Time: " << (double)(clock() - start) / CLOCKS_PER_SEC << "s\n";
  return 0;
}
