#include<iostream>
#include<atcoder/modint>
using namespace std;
using mint=atcoder::modint998244353;
int N;
long T[3<<17],v[3<<17];
main()
{
	cin>>N;
	mint n=0;
	for(int i=0;i<N;i++)
	{
		cin>>T[i]>>v[i];
		n+=T[i];
	}
	mint p=0,ans=0;
	for(int i=0;i<N;i++)
	{
		mint now;
		now-=n*p*(p+1)*(2*p+1)/6;
		now-=(n+1)*p*(p+1)/2;
		now+=p*p*(p+1)*(p+1)/4;
		p+=T[i];
		now+=n*p*(p+1)*(2*p+1)/6;
		now+=(n+1)*p*(p+1)/2;
		now-=p*p*(p+1)*(p+1)/4;
		ans+=now*v[i];
	}
	cout<<(ans/2).val()<<endl;
}