import sys
input = sys.stdin.readline

from bisect import *
from copy import deepcopy
def compress(lst):
    """
    B: lstを座圧したリスト
    D: 元の値からindex取得する辞書
    """
    B = []
    D = dict()
    vals = deepcopy(lst)
    vals = list(set(vals))
    vals.sort()
    for i in range(len(lst)):
        ind = bisect_left(vals, lst[i])
        B.append(ind)
    for i in range(len(B)):
        D[lst[i]] = B[i]
    return B, D, vals

N = int(input())
B, C = [0] * N, [0] * N
for i in range(N):
    B[i], C[i] = map(int, input().split())
    B[i] -= 1
    
A, _, vals = compress(B + C)
B2, C2 = A[:N], A[N:]
M = len(vals)
L1, L2 = [0] * M, [0] * M
mod = 998244353
for i in range(N):
    inv1 = pow(C[i] - B[i], mod - 2, mod)
    inv2 = pow((C[i] - B[i]) ** 2, mod - 2, mod)
    L1[B2[i]] += inv1
    L1[C2[i]] -= inv1
    L2[B2[i]] += inv2
    L2[C2[i]] -= inv2
    
Ac1 = [0] * M
Ac2 = [0] * M
Ac1[0] = L1[0]
Ac2[0] = L2[0]
for i in range(M - 1):
    Ac1[i + 1] = Ac1[i] + L1[i + 1]
    Ac2[i + 1] = Ac2[i] + L2[i + 1]
    
ans1 = N * (N - 1)//2
inv = pow(2, mod - 2, mod)
for i in range(M - 1):
    ans1 -= (vals[i + 1] - vals[i]) * (Ac1[i] ** 2 - Ac2[i]) * inv
    ans1 %= mod
    
for i in range(1, N + 1):
    ans1 *= i
    ans1 %= mod
    
print(ans1 * inv % mod)