#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define F first
#define S second
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n;
cin>>n;
vector<pair<ll, ll>> a(n);
for(auto &i : a) {
cin>>i.F>>i.S;
}
sort(a.begin(), a.end());
vector<ll> p(n);
p[0] = a[0].S;
for(int i=1;i<n;++i) {
p[i] = p[i - 1] + a[i].S;
}
ll mn = LLONG_MAX, ans = 0;
vector<int> best(n);
for(int i=0;i<n;++i) {
ll cur = (i == 0 ? 0 : p[i - 1]) - a[i].F;
mn = min(cur, mn);
ans = max(ans, (p[i] - a[i].F) - mn);
}
cout<<ans<<'\n';
return 0;
}
