#include <iostream>
#include <vector>
#include <bitset>
#include <queue>
#include <algorithm>
#include <cstring>
#include <cmath>
#include <stack>
#include <set>
#include <map>
#include <cassert>
#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define ll long long
#define ii pair<long long int, long long int>
#define pll pair<long long, long long>
#define fi first
#define se second
#define r first
#define c second
#define all(x) x.begin(), x.end()
#define mk(x, y) make_pair(x, y)
ostream& operator << (ostream& os, pair<int, int> a) {
return os << a.first << " : " << a.second;
}
#define endl '\n'
#define db(val) "["#val" = "<<(val)<<"] "
#define cntbit(x) __builtin_popcount(x)
const int N = 2e5 + 5;
const int iINF = 1e9;
const ll MOD = 1e9 + 7;
const ll MOD2 = 998244353;
const ll INF = 1e18;
int n;
ii a[N];
ll dp[N];
int main() {
ios_base::sync_with_stdio();
#ifdef CHUNGDINH
freopen("main.inp","r",stdin);
freopen("main.out","w",stderr);
#endif
cin >> n;
for (int i = 1; i <= n; i++) cin >> a[i].first >> a[i].second;
sort(a + 1, a + n + 1);
ll ff = -INF;
for (int i = 1; i <= n; i++) {
dp[i] = a[i].second;
dp[i] = max(dp[i], ff + a[i].second - a[i].first);
ff = max(ff, dp[i] + a[i].first);
}
cout << *max_element(dp + 1, dp + n + 1);
}
/*
Array bounds *
long long vs int
Garbage value
Sometimes, VNOI views "arrays out of bounds" as "wrong answer"
*/
