#include<iostream>
#include <bits/stdc++.h>

#define ld long double
#define ll long long
#define rep(i, a, b) for(int i = a ; i < b ; i ++)
#define sz(v) (int)v.size()
#define all(v) begin(v), end(v)
#define IO ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
using namespace std;


void doWork() {
    int n;
    cin >> n;
    vector<pair<int, int> > v(n);
    for (int i = 0; i < n; i++) {
        cin >> v[i].first >> v[i].second;
    }
    sort(v.begin(), v.end(), [&](pair<int, int> a, pair<int, int> b) {
        if (a.second - a.first >= 0 && b.second - b.first >= 0) {
            return a.first < b.first;
        }
        if (a.second - a.first < 0 && b.second - b.first < 0) {
            return a.second - b.first > b.second - a.first;
        }
        return a.second > b.second;
    });
    ll ans = 0;
    ll cur = 0;
    for (auto i: v) {
        cur -= i.first;
        ans = min(ans, cur);
        cur += i.second;
    }
    cout << -ans;
}

int main() {
    IO
    int t = 1;
//    cin >> t;
    for (int i = 1; i <= t; i++) {
        //  cout << "Case #" << i << ": ";
        doWork();
    }
}