#include <bits/stdc++.h>
using namespace std;

int main()
{
	int N;
	cin >> N;
	vector<long long> A( N * 2 );
	for( int i = 0; i < N * 2; i++ ) {
		cin >> A[i];
	}

	vector<long long> l( N );
	vector<long long> r( N );
	int j = 0;
	for( int i = 0; i < N; i++ ) {
		l[i] = A[j] - A[j + 1];
		j += 2;
	}
	j = N * 2 - 1;
	for( int i = N - 1; i >= 0; i-- ) {
		r[i] = A[j] - A[j - 1];
		j -= 2;
	}
	vector<long long> lacc( N + 1 );
	vector<long long> racc( N + 1 );
	for( int i = 0; i < N; i++ ) {
		lacc[i + 1] = lacc[i] + l[i];
	}
	for( int i = N - 1; i >= 0; i-- ) {
		racc[i] = racc[i + 1] + r[i];
	}
	long long ans = 0;
	for( int i = 0; i < N + 1; i++ ) {
		ans = max( ans,  lacc[i] + racc[i] );
	}

	cout << ans << endl;
}