#include <bits/stdc++.h>
using namespace std;
const long long MOD = 998244353;
long long modpow(long long a, long long b){
	long long ans = 1;
	while (b > 0){
		if (b % 2 == 1){
			ans *= a;
			ans %= MOD;
		}
		a *= a;
		a %= MOD;
		b /= 2;
	}
	return ans;
}
long long modinv(long long a){
	return modpow(a, MOD - 2);
}
int main(){
  int N, X;
  cin >> N >> X;
  vector<long long> x(N), y(N);
  for (int i = 0; i < N; i++){
    cin >> x[i] >> y[i];
  }
  long long ans = 0;
  vector<vector<long long>> dp(2, vector<long long>(N + 1, 0));
  for (int j = 0; j < N; j++){
    dp[0][0] = 1;
    dp[1][0] = 0;
    for (int i = 0; i < N; i++){
      if (i == j){
        dp[0][i + 1] = dp[0][i];
        dp[1][i + 1] = dp[1][i];
      } else {
        long long P = (X - x[i] + MOD) * modinv(x[j] - x[i] + MOD) % MOD;
        dp[0][i + 1] = dp[0][i] * P % MOD;
        dp[1][i + 1] = (dp[1][i] * P + dp[0][i]) % MOD;
      }
    }
    ans += dp[1][N] * y[j] % MOD;
  }
  ans %= MOD;
  cout << ans << endl;
}