#include <bits/stdc++.h>
using namespace std;
#define int long long
signed main() {
iostream::sync_with_stdio(false);
cin.tie(nullptr);cout.tie(nullptr);
int N, sum = 0;cin >> N;
vector<pair<int,int>> A(N);for(auto &e : A)cin >> e.first >> e.second;
sort(A.begin(), A.end());
vector<int> suf(N);
suf[N - 1] = A[N - 1].first;
for(int i = N - 2;i>=0;i--){
sum += A[i + 1].second;
suf[i] = A[i].first + sum;
suf[i] = min(suf[i], suf[i + 1]);
}
sum += A[0].second;
int pref = 0;
int ans = 0;
for(int i = 0;i<N;i++){
ans = max(ans, sum - pref - suf[i] + A[i].first);
pref += A[i].second;
}
cout << ans << "\n";
}
