#include<bits/stdc++.h>
using namespace std;
#define int long long
#define pb push_back
#define pii pair<int,int>
#define fi first
#define se second
int n;
vector<pii> a;
vector<int> val;
int get(int x,int y){
return val[y+1]-val[x];
}
void solve(){
cin>>n;
a.resize(n);val.resize(n+2);
for(auto&x:a) cin>>x.first>>x.second;
sort(a.begin(),a.end());
for(int i=1;i<=n;i++) val[i]=val[i-1]+a[i-1].second;
int mx=0,ans=0;
for(int i=0;i<n;i++){
mx=max(mx,a[i].first-get(0,i-1));
ans=max(ans,get(0,i)-a[i].first+mx);
}
cout<<ans<<'\n';
}
signed main(){
ios_base::sync_with_stdio(0); cin.tie(0);
solve();
}
