#include <bits/stdc++.h>
#define int long long
using namespace std;
const int N=2010,P=998244353;
int n,k,x[N],y[N];
int c[N]; 
inline int read()
{
	int x=0,f=1;char ch=getchar();
	while (ch<'0'||ch>'9'){if (ch=='-') f=-1;ch=getchar();}
	while (ch>='0'&&ch<='9'){x=x*10+ch-48;ch=getchar();}
	return x*f;
}

signed main(){
	std::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];
	}
	int sum=0;
	for(int i=1;i<=n;i++){
		int p1=1,p2=1;
		for(int j=1;j<=n;j++){
			if(j!=i){
				p1=1ll*p1*(k-x[j]+P)%P;
				p2=1ll*p2*(x[i]-x[j]+P)%P;
			}
		}
		sum=1ll*(1ll*sum%P+1ll*p1*y[i]/1ll*p2%P+P)%P;
	}
	cout<<1ll*sum;
	return 0;
}
/*
10 10773
13654 13678
21667 29551
28358 8123
2143 15198
3770 10543
23113 10196
11752 30931
24922 1345
6306 5328
14114 4669

*/
/*
41359329

*/