p4781

using namespace std;

typedef long long ll;
const int maxn = 2020;
const ll mod = 998244353;
int n, k;
ll x[maxn], y[maxn], a[maxn], inv[maxn][maxn];

ll (ll q, ll w){
    ll ret = 1;
    while(w){
        if(w & 1) ret = ret * q % mod;
        q = q * q % mod;
        w >>= 1;
    }
    return ret;
}

int main(){
    ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
    cin >> n >> k;
    for(int i = 1; i <= n; i++) cin >> x[i] >> y[i];
    for(int i = 1; i <= n; i++){
        for(int j = 1; j <= n; j++){
            inv[i][j] = pow_mod((x[i] - x[j]) % mod + mod, mod - 2);
        }
    }
    for(int i = 1; i <= n; i++){
        a[i] = y[i];
        for(int j = 1; j <= n; j++){
            if(i == j) continue;
            a[i] = a[i] * inv[i][j] % mod;
        }
    }
    ll res = 0;
    for(int i = 1; i <= n; i++){
        ll ans = a[i];
        for(int j = 1; j <= n; j++){
            if(i == j) continue;
            ans = ans * ((k - x[j]) % mod + mod) % mod;
        }
        res = (res + ans) % mod;
    }
    cout << res << 'n';
    return 0;
}