#include <iostream>
#include <cstring>
#include <algorithm>
#include <vector>
#include <utility>
#include <cmath>
#include <ctime>
#include <cassert>
#include <set>
#include <stack>
#include <map>
#include <queue>
#include <random>
#include <chrono>
#include <bitset>
#include <array>
using ll = long long;
#define debug(x) cout << #x << " = " << x << '\n'
#define separator "===============================================\n"
#define all(a) a.begin(), a.end()
#define SZ(a) (int)(a).size()
using namespace std;
const int mxn = 1e5 + 3;
const ll  mod = 1e9 + 7;
const int inf32 = 2e9;
const ll  inf64 = 3e18;
// #pragma GCC optimize("O3,unroll-loops")
// #pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
void solve(){
    int n; cin >> n;
    vector<pair<ll, ll>> a(n);
    for (int i = 0; i < n; ++i)
        cin >> a[i].first >> a[i].second;
    sort(all(a));
    ll res = -inf64, pref = 0, mx_pref = -inf64;
    for (int i = 0; i < n; ++i){
        mx_pref = max(mx_pref, -pref + a[i].first);
        pref += a[i].second;
        res = max(res, pref - a[i].first + mx_pref);
    }
    cout << res;
}
int main(){
	auto start = chrono::steady_clock::now();
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int t = 1;
    // cin >> t;
    while(t--) solve();
    chrono::duration<double> elapsed {chrono::steady_clock::now() - start};
    cerr << "\n>> Runtime: " << elapsed.count() << "s\n";
}
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