#include <bits/stdc++.h>
using namespace std;
#define ll long long
int main() {
int n;
cin >> n;
vector<pair<ll,ll>>vec(n);
for(int i = 0;i < n;i++){
cin >> vec[i].first >> vec[i].second;
}
sort(vec.begin(),vec.end());
ll best = 0;
ll sum = 0;
ll mx = LLONG_MIN;
for(int i = 0;i < n;i++){
ll pre = sum + vec[i].second;
mx = max(mx,pre - vec[i].first + best);
best = max(best,vec[i].first - sum);
sum = pre;
}
cout << mx;
}
/*
S - A[i] + A[j]
Pre[i] - pre[j-1] - A[i] + A[j]
pre[i] - A[i] + max( - pre[j-1] + A[j])
*/
