#include <stdio.h>
#include <algorithm>
#include <assert.h>
#include <bitset>
#include <cmath>
#include <complex>
#include <deque>
#include <functional>
#include <iostream>
#include <limits.h>
#include <map>
#include <math.h>
#include <queue>
#include <set>
#include <stdlib.h>
#include <string.h>
#include <string>
#include <time.h>
#include <unordered_map>
#include <unordered_set>
#include <vector>

#pragma warning(disable:4996)
#pragma comment(linker, "/STACK:336777216")
using namespace std;

#define mp make_pair
#define all(x) (x).begin(), (x).end()
#define ldb ldouble

typedef tuple<int, int, int> t3;
typedef long long ll;
typedef unsigned long long ull;
typedef double db;
typedef long double ldb;
typedef pair <int, int> pii;
typedef pair <ll, ll> pll;
typedef pair <ll, int> pli;
typedef pair <db, db> pdd;

int IT_MAX = 1 << 18;
int MOD = 1000000007;
const int INF = 0x3f3f3f3f;
const ll LL_INF = 0x3f3f3f3f3f3f3f3f;
const db PI = acos(-1);
const db ERR = 1e-10;
#define szz(x) (int)(x).size()
#define rep(i, n) for(int i=0;i<n;i++)
#define Se second
#define Fi first

const int MX = 200005;
const int MM = 1000000007;

ll A[MX], B[MX];
int N;

ll DnC(int s, int e){
	if( s > e ) return 0;
	if( s == e ) return B[s];
	int m = (s+e) / 2;
	ll l = 0, total = 0, r = 0;
	for(int i = m; i >= s; i--){
		total += B[i];
		l = max(l, total - A[m] + A[i]);
	}
	total = 0;
	for(int i = m; i <= e; i++){
		total += B[i];
		r = max(r, total - A[i] + A[m]);
	}
	return max({DnC(s, m-1), DnC(m+1, e), l+r-B[m]});
}

int main()
{
	scanf("%d", &N);
	for(int i = 1; i <= N; i++) scanf("%lld%lld", A+i, B+i);
	printf("%lld\n", DnC(1, N));
}
