MOD = 998244353
n = int(input())
T = [0]*n
V = [0]*n
for i in range(n):
    T[i],V[i] = map(int,input().split())
for i in range(1,n):
    T[i] += T[i-1]
    T[i] %= MOD
for i in range(n):
    T[i] -= 1

M = T[-1]+1
def f(n):
    return (n+1)*(n+2)%MOD*(n+3)%MOD*(4*M-3*n)%MOD

ans = 0
for i in range(n):
    c = f(T[i])
    if i: c -= f(T[i-1])
    ans += V[i]*c
    ans %= MOD

print(ans*291154603%MOD)