#include <bits/stdc++.h>
using namespace std;
#define lalala ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define int long long int
#define N 500005
#define big 100000000000000000
#define endl "\n"
#define pb push_back
#define p push
#define f first
#define s second
int pre[N];
signed main() {
//lalala;
int n;cin>>n;
vector<pair<int,int>> v;
for(int i=0;i<n;i++){
int a,b;cin>>a>>b;
v.pb({a,b});
}
v.pb({-1,-1});
sort(v.begin(),v.end());
priority_queue<int> pq;
int ans=0;
for(int i=1;i<=n;i++){
pre[i]=pre[i-1]+v[i].s;
int s2=pre[i-1], s1=pre[i];
pq.p(v[i].f-s2);
int deg=pq.top();
ans=max(ans,s1-v[i].f+deg);
}
cout<<ans<<endl;
}
