MOD = 998244353
N = int(input())
T = [None] * N
V = [None] * N
S = [0] * (N + 1)
for i in range(N):
	T[i], V[i] = map(int, input().split())
	T[i] %= MOD
	S[i + 1] = (S[i] + T[i]) % MOD

ans = 0
for i in range(N):
	a = 0
	a -= 3 * T[i] ** 2 % MOD * ((T[i] + 1) ** 2 % MOD) % MOD
	a += 2 * (S[N] - 3 * S[i]) * T[i] % MOD * (T[i] + 1) % MOD * (2 * T[i] +
	                                                                1) % MOD
	a += 6 * (2 * S[N] * S[i] - 3 * S[i] ** 2 + S[N] + 1) % MOD * T[i] % MOD * (T[i] + 1) % MOD
	a += 12 * (S[N] * S[i] - S[i] ** 2 + S[N] + 1) % MOD * S[i] % MOD * T[i] % MOD
	ans += a % MOD * V[i]
	ans %= MOD

ans = ans * pow(24, MOD - 2, MOD) % MOD

print(ans)