#include<cstdio>#include<cstring>usingnamespace std;#define N 2010#define md 998244353#define ll long longstruct{
ll x, y;}a[N];
ll ksm(ll x, ll y){if(!y)return1;
ll l =ksm(x, y /2);if(y %2)return l * l % md * x % md;return l * l % md;}intmain(){int n, i, j;
ll k;scanf("%d%lld",&n,&k);for(i =1; i <= n; i++){scanf("%lld%lld",&a[i].x,&a[i].y);}
ll ans =0;for(i =1; i <= n; i++){
ll t = a[i].y, s =1;for(j =1; j <= n; j++)if(j != i){
s = s *(a[i].x - a[j].x)% md;
t = t *(k - a[j].x)% md;}
ans =(ans + t *ksm(s, md -2))% md;}printf("%lld",(ans % md + md)% md);return0;}