#include <bits/stdc++.h>
using namespace std;
const long long MOD = 998244353;
long long modpow(long long a, long long b){
	long long ans = 1;
	while (b > 0){
		if (b % 2 == 1){
			ans *= a;
			ans %= MOD;
		}
		a *= a;
		a %= MOD;
		b /= 2;
	}
	return ans;
}
long long modinv(long long a){
	return modpow(a, MOD - 2);
}
int main(){
  int N;
  cin >> N;
  vector<long long> T(N), V(N);
  for (int i = 0; i < N; i++){
    cin >> T[i] >> V[i];
  }
  vector<long long> C(N + 1);
  C[0] = 0;
  for (int i = 0; i < N; i++){
    C[i + 1] = (C[i] + T[i]) % MOD;
  }
  vector<long long> S(N + 1, 0);
  for (int i = 0; i <= N; i++){
    long long a = MOD - modinv(2);
    long long b = C[N] * modinv(2) % MOD;
    long long c = (C[N] + 1) * modinv(2) % MOD;
    S[i] += C[i] * (C[i] + 1) % MOD * modinv(2) % MOD * c % MOD;
    S[i] += C[i] * (C[i] + 1) % MOD * (C[i] * 2 + 1) % MOD * modinv(6) % MOD * b % MOD;
    S[i] += C[i] * C[i] % MOD * (C[i] + 1) % MOD * (C[i] + 1) % MOD * modinv(4) % MOD * a % MOD;
    S[i] %= MOD;
  }
  vector<long long> S2(N);
  for (int i = 0; i < N; i++){
    S2[i] = (S[i + 1] - S[i] + MOD) % MOD;
  }
  long long X = 0;
  for (int i = 0; i < N; i++){
    X += S2[i] * V[i] % MOD;
  }
  X %= MOD;
  cout << X << endl;
}