#include <bits/stdc++.h>
#define int long long
using namespace std;
const int N = 5e5 + 5;
int n;
pair<int,int> a[N];
int pre[N];
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
cin >> n;
for(int i = 1; i <= n; i++) cin >> a[i].first >> a[i].second;
sort(a + 1, a + n + 1);
for(int i = 1; i <= n; i++){
pre[i]=pre[i-1]+ a[i].second;
}
int amin = 0, res = 0;
for(int i = 1; i <= n; i++){
amin= max(amin, a[i].first - pre[i-1]);
res = max(res, pre[i] - a[i].first + amin);
}
cout << res << "\n";
}
