#include <cstdio>
#include <iostream>
#include <string>
#include <sstream>
#include <stack>
#include <algorithm>
#include <cmath>
#include <queue>
#include <map>
#include <set>
#include <cstdlib>
#include <bitset>
#include <tuple>
#include <assert.h>
#include <deque>
#include <bitset>
#include <iomanip>
#include <limits>
#include <chrono>
#include <random>
#include <array>
#include <unordered_map>
#include <functional>
#include <complex>

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

const long long MAX = 5100000;
const long long INF = 1LL << 60;
const int inf = 1 << 28;
const long long mod = 1000000007LL;
//const long long mod = 998244353LL;

using namespace std;
typedef unsigned long long ull;
typedef long long ll;

int main()
{
	/*
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	*/
	ll N; scanf("%lld", &N);
	vector<ll> a(N * 2); for (ll i = 0; i < N * 2; i++) scanf("%lld", &a[i]);
	vector<ll> sum1(N + 1), sum2(N + 1);
	for (ll i = 0; i < N * 2; i += 2) {
		sum1[i/2 + 1] = sum1[i/2] + a[i] - a[i + 1];
		sum2[i/2 + 1] = sum2[i/2] + a[i + 1] - a[i];
	}
	ll res = -INF;
	for (int i = 0; i <= N; i++) {
		chmax(res, sum1[i] + sum2[N] - sum2[i]);
	}
	cout << res << endl;
	return 0;
	/*
		おまじないを使ったらscanfとprintf関連注意！！！！！！！！！！！！
	*/
}