#include<iostream>
#include<string>
#include<iomanip>
#include<cmath>
#include<vector>
#include<algorithm>

using namespace std;

#define int long long
#define endl "\n"

constexpr long long INF = (long long)1e18;
constexpr long long MOD = 1'000'000'007; 

signed main(){
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	cout<<fixed<<setprecision(10);
	
	int N;
	int ans = -INF;
	vector<int> A, sum, sum2;
	
	cin>>N;
	
	A.resize(N*2);
	sum.resize(N+1);
	sum2.resize(N+1);
	
	for(int i = 0; i < N * 2; i++){
		cin>>A[i];
		
		if(i%2 == 0) {
			sum[i/2+1] += A[i];
			sum2[i/2] -= A[i]; 
		} else {
			sum[i/2+1] -= A[i];
			sum2[i/2] += A[i]; 
		}
	}
	
	for(int i = 0; i < N; i++){
		sum[i+1] += sum[i];
	}
	
	for(int i = N; i > 0; i--){
		sum2[i-1] += sum2[i];
	}
	
	for(int i = 0; i <= N; i++){
		// cout<<"i = "<<i<<" "<<sum[i]<<" "<<sum2[i]<<endl;
		ans = max(ans, sum[i] + sum2[i]);
	}
	
	cout<<ans<<endl;
	
	return 0;
}