#include <bits/stdc++.h>
using namespace std;
long long pref[500007];
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
vector<pair<long long, long long>> prace;
prace.push_back({0, 0});
long long n, odp = 0, maxx = LLONG_MIN;
cin >> n;
for(int i = 0; i < n; i++)
{
long long x, y;
cin >> x >> y;
prace.push_back({x, y});
}
sort(prace.begin(), prace.end());
for(int i = 1; i <= n; i++)
{
pref[i] = pref[i - 1] + prace[i].second;
}
for(int i = 1; i <= n; i++)
{
maxx = max(maxx, prace[i].first - pref[i - 1]);
odp = max(odp, maxx + pref[i] - prace[i].first);
}
cout << odp << endl;
return 0;
}
