//Arayi
#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <string>
#include <queue>
#include <stack>
#include <algorithm>
#include <math.h>
#include <vector>
#include <cstring>
#include <ctime>
#include <set>
#include <bitset>
#include <map>
#include <unordered_map>
#include <unordered_set>
#include <iomanip>
#include <ctime>
#include <climits>
#include <cassert>
#include <chrono>
#include <random>
#include <complex>
#define fr first
#define sc second
#define MP make_pair
#define ad push_back
#define PB push_back
#define fastio ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define lli long long int
#define y1 arayikhalatyan
#define j1 jigglypuff
#define ld long double
#define itn int
#define pir pair<int, int>
#define all(x) (x).begin(), (x).end()
#define str string
#define enl endl
#define en endl
#define cd complex<long double>
#define vcd vector<cd>
#define vii vector<int>
#define vlli vector<lli>
using namespace std;
lli gcd(lli a, lli b) { return (b == 0LL ? a : gcd(b, a % b)); }
ld dist(ld x, ld y1, ld x2, ld y2)
{
return sqrt((x - x2) * (x - x2) + (y1 - y2) * (y1 - y2));
}
lli S(lli a)
{
return (a * (a + 1LL)) / 2LL;
}
mt19937 rnd(363542);
char vow[] = { 'a', 'e', 'i', 'o', 'u' };
int dx[] = { 0, -1, 0, 1, -1, -1, 1, 1, 0 };
int dy[] = { -1, 0, 1, 0, -1, 1, -1, 1, 0 };
const int N = 5e5 + 30;
const lli mod = 998244353;
const ld pi = acos(-1);
const ld e = 1e-13;
lli bp(lli a, lli b = mod - 2LL)
{
lli ret = 1;
while (b)
{
if (b & 1) ret *= a, ret %= mod;
a *= a;
a %= mod;
b >>= 1;
}
return ret;
}
ostream& operator<<(ostream& c, pir a)
{
c << a.fr << " " << a.sc;
return c;
}
struct pt
{
lli x, y;
int ind;
int bl;
bool operator==(const pt& a)
{
return ind == a.ind;
}
bool operator<(const pt& b)
{
if (x == b.x) return y < b.y;
return x < b.x;
}
};
itn n;
pair<lli, lli> a[N];
lli pat, mx[N];
int main()
{
fastio;
cin >> n;
for (int i = 1; i <= n; i++)
{
cin >> a[i].fr >> a[i].sc;
}
sort(a + 1, a + n + 1);
for (int i = 1; i <= n; i++)
a[i].sc += a[i - 1].sc;
for (int i = n; i > 0; i--)
{
mx[i] = a[i].sc - a[i].fr;
if (i < n)mx[i] = max(mx[i], mx[i + 1]);
pat = max(pat, mx[i] + a[i].fr - a[i - 1].sc);
}
cout << pat << endl;
return 0;
}
/*
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*(><)*
\/ /
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/\
/ \
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*/
