import sys
input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
sys.setrecursionlimit(10**7)
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################
mod = 998244353
n,X = na()
x,y = zip(*[na() for i in range(n)])

lrui = [1]*(n+1)
rrui = [1]*(n+1)

for i in range(n):
    lrui[i+1] = lrui[i] * (X-x[i]) % mod
for i in range(n-1,-1,-1):
    rrui[i] = rrui[i+1] * (X-x[i]) % mod

dxs = [1] * n
for i in range(n):
    for j in range(n):
        if i==j:continue
        dxs[i] *= x[i] - x[j]
        dxs[i] %= mod

for i in range(n):
    dxs[i] = pow(dxs[i],mod-2,mod)
a,b,c = 0,0,0
for i in range(n):
    a += y[i] * lrui[i] * rrui[i+1] * dxs[i]
    a %= mod
a *= n
for i in range(n):
    b += y[i] * dxs[i]
    b %= mod
    c += lrui[i] * rrui[i+1]
    c %= mod

print((a-b*c)%mod)