#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e5 + 5;
typedef long long ll;
signed main(){
int N; cin >> N;
pair<ll, ll> A[N+1];
priority_queue<pair<ll, int> > pq;
for(int i=1; i<=N; i++){
cin >> A[i].first >> A[i].second;
}
sort(A+1, A+N+1);
ll ps[N+1];
ps[0] = 0;
for(int i=1; i<=N; i++){
ps[i] = ps[i-1] + A[i].second;
}
ll S = 0;
for(int i=2; i<=N; i++){
S = S + A[i].second - A[i].first + A[i-1].first;
pq.push({S, i});
}
ll ans = 0;
for(int i=1; i<=N; i++){
ans = max(ans, A[i].second);
}
for(int i=1; i<=N; i++){
while(pq.top().second<i) pq.pop();
if(pq.size()) ans = max(ans, ps[pq.top().second] - ps[i-1] - A[pq.top().second].first + A[i].first);
}
cout << ans << endl;
}
