// Born_To_Laugh - Hughie Do
#include <bits/stdc++.h>
#define alle(sth) sth.begin(), sth.end()
using namespace std;
typedef long long ll;
[[maybe_unused]] const ll MOD = 998244353, INF = 1e18 + 7;
#define int ll
void solve(){
int n;cin >> n;
vector<pair<int,int>> a(n);
for(int i=0; i<n; ++i){
cin >> a[i].first >> a[i].second;
}
sort(alle(a));
vector<int> pref(n);
pref[0] = a[0].second;
for(int i=1; i<n; ++i){
pref[i] = pref[i-1] + a[i].second;
}
int ans = 0;
for(int i=0; i<n; ++i)ans = max(ans, a[i].second);
int x = -INF;
for(int j=1; j<n; ++j){
int num = a[j-1].second + a[j-1].first - pref[j-1];
x = max(x, num);
int res = a[j].second - a[j].first + pref[j-1];
res += x;
ans = max(ans, res);
}
cout << ans << '\n';
}
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
solve();
}
