#include <iostream>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <ctime>
#include <deque>
#include <ctime>
#include <string>
#include <algorithm>
#include <vector>
#include <bitset>
#include <cassert>
#include <cstring>
#include <queue>

#define fi first
#define se second
#define ll long long
#define pii pair<int, int>
#define pil pair<int, long long>
#define pli pair<long long, int>
#define pll pair<long long, long long>
#define mp(x, y) make_pair((x), (y))

using namespace std;
const ll MOD = 1000 * 1000 * 1000 + 7;
const int MAXSZ = 5e5 + 100;

ll stab(ll a) {
    return ((a % MOD + MOD) % MOD);
}

int main() {
    freopen("kebab.in", "r", stdin);
    freopen("kebab.out", "w", stdout);
    ios::sync_with_stdio(false);
    cout.tie(0); cin.tie(0);

    int n, t;
    cin >> n >> t;

    vector<vector<ll>> fdp(301, vector<ll>(301, 0));
    for (int i = 1; i < 301; ++i) {
        fdp[1][i] = 1;
    }

    for (int i = 2; i < 301; ++i) {
        for (int l = 2; l < 301; ++l) {
            for (int j = 1; j <= i - t - 1; ++j) {
                fdp[i][l] += fdp[j][l - 1];
            }
            fdp[i][l] = stab(fdp[i][l]);
        }
    }

    array<ll, MAXSZ> dp;
    int cur_s = 1;
    dp[0] = 1;
    for (int i = 0; i < n; ++i) {
        int q, x;
        cin >> q >> x;

        for (int j = cur_s; j < cur_s + q; ++j) {
            dp[j] = dp[j - 1];
            for (int l = cur_s; l <= j; ++l) {
                dp[j] += fdp[j - l + 1][q - x] * dp[max(0, min(cur_s - 1, l - t - 1))];
                dp[j] = stab(dp[j]);
            }
        }

        cur_s += q;
    }
    cout << dp[cur_s - 1] << endl;

    r