#include <bits/stdc++.h>
using namespace std;
using ll=long long;
#define in insert
#define pb push_back
#define pll pair<ll,ll>
void solve(){
ll n;
cin>>n;
vector<pll>v;
pair<ll,ll>p;
for(int i=0;i<n;i++){
cin>>p.first>>p.second;
v.pb(p);
}
sort(v.begin(),v.end());
vector<ll>pre(n+1,0);
for(int i=1;i<=n;i++){
pre[i]=pre[i-1]+v[i-1].second;
}
vector<ll>a(n+2,0);
for(int i=1;i<=n;i++){
a[i]=pre[i]-v[i-1].first;
}
vector<ll>suff(n+2,0);
for(int i=n;i>=1;i--){
suff[i]=max(suff[i+1],a[i]);
}
ll ans=0;
ll temp;
ll sum=0;
for(int i=1;i<=n;i++){
temp=suff[i]+v[i-1].first-pre[i-1];
ans=max(ans,temp);
}
cout<<ans;
}
int main(){
solve();
return 0;
}
