#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pll pair<int, int>
#define mp make_pair
#define pb push_back
#define f first
#define s second
#define endl '\n'
signed main(){
int n;cin>>n;
vector<pair<int,int>> v(n);
int ans=0;
for(int i=0;i<n;i++){
cin>>v[i].f>>v[i].s;
ans=max(ans,v[i].s);
}
sort(v.begin(),v.end());
vector<int> sfx(n, 0);
sfx[n-1]=v[n-2].f-v[n-1].f+v[n-1].s;
for(int i=n-2;i>=1;i--){
sfx[i]=sfx[i+1]+v[i].s-v[i].f+v[i-1].f;
}
//~ for(int i=1;i<n;i++){
//~ cout<<sfx[i]<<" ";
//~ }
//~ cout<<endl;
int best=0;
for(int i=n-2;i>=0;i--){
best=min(best, sfx[i+1]);
ans=max(ans, v[i].s+sfx[i+1]-best);
}
cout<<ans;
}
