import sys
input = sys.stdin.buffer.readline
sys.setrecursionlimit(10 ** 7)

mod = 998244353
div2 = pow(2, mod-2, mod)
div4 = pow(4, mod-2, mod)
div6 = pow(6, mod-2, mod)

N = int(input())
TV = []
total = 0
for _ in range(N):
    t, v = map(int, input().split())
    t %= mod
    total += t
    total %= mod
    TV.append((t, v))


def F(n):
    x = (total + 1) * n * (n + 1) % mod
    y = total * n * (n + 1) * (2 * n + 1) % mod
    z = n * n * (n + 1) * (n + 1) % mod
    return (x * div2 % mod + y * div6 % mod - z * div4 % mod) * div2 % mod


ans = 0
cnt = 0
for t, v in TV:
    x = F(cnt + t) - F(cnt)
    ans += v * x % mod
    ans %= mod
    cnt += t
    cnt %= mod
print(ans)