#include <bits/stdc++.h>
using namespace std;
using ll=long long;
ll compute(ll sum,ll min,ll max){
return sum-(max-min);
}
int main(){
int n;
cin>>n;
vector<pair<ll,ll>> paintings(n);
for (int i=0;i<n;i++){
ll a,b;
cin>>a>>b;
paintings[i]={a,b};
}
sort(paintings.begin(),paintings.end());
ll l=0;
ll r=-1;
ll ans=0;
ll sum=0;
ll min=paintings[l].first;
ll maxx=0;
while (r<n-1){
r++;
sum+=paintings[r].second;
maxx=paintings[r].first;
ll now=compute(sum,min,maxx);
ans=max(ans,now);
ll sumWithoutL=sum-paintings[l].second;
ll minWithoutL=paintings[l+1].first;
ll ansWithoutL=compute(sumWithoutL,minWithoutL,maxx);
while (l<r && ansWithoutL>now){
sum=sumWithoutL;
min=minWithoutL;
l++;
sumWithoutL=sum-paintings[l].second;
minWithoutL=paintings[l+1].first;
ansWithoutL=compute(sumWithoutL,minWithoutL,maxx);
}
ans=max(ans,compute(sum,min,maxx));
}
cout<<ans;
return 0;
}
