#include <bits/stdc++.h>
using namespace std;
#define int long long
#define OYY LLONG_MAX
#define faster ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define fi first
#define se second
#define FOR for(int i=1;i<=n;i++)
#define mid (start+end)/2
#define pb push_back
#define lim 500005
const int mod=998244353;
int n;
int dizi[lim][2];
int pre[lim];
int tree[4*lim];
inline void update(int node,int start,int end,int l,int r,int val){
if(start>end || start>r || end<l)return ;
if(start>=l && end<=r){
tree[node]=val;
return ;
}
update(node*2,start,mid,l,r,val),update(node*2+1,mid+1,end,l,r,val);
tree[node]=max(tree[node*2],tree[node*2+1]);
}
inline int query(int node,int start,int end,int l,int r){
if(start>end || start>r || end<l)return 0;
if(start>=l && end<=r)return tree[node];
return max(query(node*2,start,mid,l,r),query(node*2+1,mid+1,end,l,r));
}
int32_t main(){
faster
cin>>n;
vector<pair<int,int>> v;
FOR{
cin>>dizi[i][0]>>dizi[i][1];
v.pb({dizi[i][0],dizi[i][1]});
}
sort(v.begin(),v.end());
for(int i=0;i<n;i++){
dizi[i+1][0]=v[i].fi;
dizi[i+1][1]=v[i].se;
}
FOR{
pre[i]=pre[i-1]+dizi[i][1];
}
FOR{
update(1,1,n,i,i,pre[i]-dizi[i][0]);
}
int cev=0;
FOR{
cev=max(cev,query(1,1,n,i,n)+dizi[i][0]-pre[i-1]);
}
cout<<cev<<'\n';
return 0;
}
