#include <bits/stdc++.h>
using namespace std;
const int N = 500009;
const int mod = 1000000007;
long long int dp[101][2][3001];
long long int a[101], b[101];
void pre() {
  for (long long int i = 0; i < 101; i++) {
    for (long long int j = 0; j < 3001; j++) {
      dp[i][0][j] = dp[i][1][j] = 0;
    }
  }
}
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  ;
  pre();
  long long int n, l;
  cin >> n >> l;
  for (long long int i = 1; i <= n; i++) {
    cin >> a[i] >> b[i];
  }
  for (long long int i = 1; i <= l; i++) {
    for (long long int j = 1; j <= n; j++) {
      for (long long int k = 0; k < 2; k++) {
        if (k == 0) {
          if (a[j] == i) {
            dp[j][0][i] = 1;
            continue;
          } else if (a[j] > i) {
            continue;
          }
        } else {
          if (b[j] == i && a[j] != b[j]) {
            dp[j][1][i] = 1;
            continue;
          } else if (b[j] > i) {
            continue;
          }
        }
        for (long long int ji = 1; ji <= n; ji++) {
          for (long long int ki = 0; ki < 2; ki++) {
            if (j == ji) continue;
            if (k == 0) {
              if (ki == 0) {
                if (a[j] == b[ji]) {
                  dp[j][k][i] += dp[ji][ki][i - a[j]];
                  dp[j][k][i] %= mod;
                }
              } else {
                if (a[j] == a[ji]) {
                  dp[j][k][i] += dp[ji][ki][i - a[j]];
                  dp[j][k][i] %= mod;
                }
              }
            } else if (a[j] != b[j]) {
              if (ki == 0) {
                if (b[j] == b[ji]) {
                  dp[j][k][i] += dp[ji][ki][i - b[j]];
                  dp[j][k][i] %= mod;
                }
              } else {
                if (b[j] == a[ji]) {
                  dp[j][k][i] += dp[ji][ki][i - b[j]];
                  dp[j][k][i] %= mod;
                }
              }
            }
          }
        }
      }
    }
  }
  long long int ans = 0;
  for (long long int i = 1; i <= n; i++) {
    ans += (dp[i][0][l] + dp[i][1][l]) % mod;
    ans %= mod;
  }
  cout << ans << "\n";
  return 0;
}
