#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 4000000000000000001LL

mint get(long long a,long long b,long long c,long long d){
	long long res = abs(a*d - b*c);
//	cout<<a<<' '<<b<<' '<<c<<' '<<d<<' '<<res<<endl;
	return mint(res)*mint(2).inv();
}
int main(){
	
	int n;
	cin>>n;
	vector<int> a(n),b(n);
	rep(i,n)cin>>a[i]>>b[i];
	mint ans = 0;
	rep(i,n-1){
		if(i==0)continue;
		ans += get(a[i]-a[0],b[i]-b[0],a[i+1]-a[0],b[i+1]-b[0]);
	}
	cout<<ans.val()<<endl;
	return 0;
}