// https://oj.uz/problem/view/JOI18_art
#include <bits/stdc++.h>
using namespace std;
#define ll long long
int main()
{
ios::sync_with_stdio(0);
cin.tie(0);
int n;
cin >> n;
pair<ll,ll> pr[n];
for(int i = 0; i < n; i++)
{
cin >> pr[i].first >> pr[i].second;
}
sort(pr,pr+n);
ll pref[n+1];
pref[0] = 0;
for(int i = 0; i <= n; i++)
{
pref[i+1] = pref[i] + pr[i].second;
}
ll lmax[n];
lmax[0] = pr[0].first;
for(int i = 1; i < n; i++)
{
lmax[i] = max(lmax[i-1], pr[i].first - pref[i]);
}
ll best = LLONG_MIN;
for(int i = 0; i < n; i++)
{
best = max(best, lmax[i] + pref[i+1] - pr[i].first);
}
cout << best;
}
/*
3
2 3
11 2
4 5
*/
