#include <bits/stdc++.h>
using namespace std;
// #pragma GCC optimize("O3,unroll-loops")
// #pragma GCC target("avx2,bmi,bmi2,popcnt,lzcnt")
using ll = long long;
using ull = unsigned long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using str = string;
using ld = long double;
using db = double;
///--------------------------------
#define F first
#define S second
#define pb push_back
#define lb lower_bound
#define ub upper_bound
#define sz(x) (int)((x).size())
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define mem(f, x) memset(f, x, sizeof(f))
#define uniqueV(x) sort(all(x)), (x).resize(unique(all(x)) - x.begin())
template<class T> bool maximize(T &a, const T &b){ return (a < b ? a = b, 1 : 0); }
template<class T> bool minimize(T &a, const T &b){ return (a > b ? a = b, 1 : 0); }
///--------------------------------
#define PROBLEM "test"
const int MOD = 1e9 + 7; // 998244353;
const ll INF = 1e18;
const ld eps = 1e-9;
const ld PI = acos(-1);
const int dx[4]{0, 1, 0, -1}, dy[4]{1, 0, -1, 0}; // R D L U
const int ddx[4]{-1, 1, 1, -1}, ddy[4]{1, 1, -1, -1}; // UR DR DL UL
///--------------------------------
void precalc();
void solve();
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
if (fopen(PROBLEM".inp", "r")) {
freopen(PROBLEM".inp", "r", stdin);
freopen(PROBLEM".out", "w", stdout);
}
constexpr bool MULTI_TEST = 0;
int t = 1;
if (MULTI_TEST) cin >> t;
while (t--)
solve();
// cerr << setprecision(3) << fixed;
// cerr << "[" << 1.0 * clock() / CLOCKS_PER_SEC << "s] ";
}
///--------------------[PROBLEM SOLUTION]--------------------///
void solve() {
ll n;
cin >> n;
vector<pll> v(n);
for (int i = 0; i < n; i++)
cin >> v[i].F >> v[i].S;
sort(all(v));
ll res = -INF, mx = -INF, pref = 0;
for (int i = 0; i < n; i++) {
maximize(mx, -pref + v[i].F);
maximize(res, (pref + v[i].S) - v[i].F + mx);
pref += v[i].S;
}
cout << res << '\n';
}
