#include<bits/stdc++.h>
using namespace std;
int n;
vector<long long> tree;
void SET(int in,long long val)
{
in+=n;
tree[in]=val;
for(;in>1;in/=2)
{
tree[in/2]=max(tree[in],tree[in^1]);
}
}
long long cal(int b,int e)
{
long long ans=0;
for(b+=n,e+=n;b<e;b/=2,e/=2)
{
if(b&2==1) ans=max(ans,tree[b++]);
if(e%2==1) ans=max(ans,tree[--e]);
}
return ans;
}
int main()
{
cin>>n;
vector<long long> pre;
vector<pair<long long,long long>> v;
tree=vector<long long>(2*n,0);
pre.push_back(0);
for(int i=0;i<n;i++)
{
long long a,b;
cin>>a>>b;
v.push_back({a,b});
}
sort(v.begin(),v.end());
for(int i=0;i<n;i++)
{
pre.push_back(pre[i]+v[i].second);
}
for(int i=0;i<n;i++)
{
SET(i,pre[i+1]-v[i].first);
}
long long ans=0;
for(int i=0;i<n;i++)
{
ans=max(ans,cal(i+1,n)-pre[i]+v[i].first);
}
cout<<ans;
}
