#include <bits/stdc++.h>
using namespace std;
#define int long long
#define yes cout<<"YES"<<endl
#define no cout<<"NO"<<endl
#define S second
#define F first
int reqemcemi(int n){
int cem=0;
while(n>0){
cem+=n%10;
n/=10;
}
return cem;
}
void solve(){
int n;
cin>>n;
vector<pair<int,int>>vt(n+1);
for(int i=1;i<=n;i++){
cin>>vt[i].F>>vt[i].S;
}
sort(vt.begin()+1,vt.end());
vector<int>a(n+1),b(n+1,0);
for(int i=1;i<=n;i++){
a[i]=vt[i].F;
b[i]=b[i-1]+vt[i].S;
}
int mine=LLONG_MAX,cvb=0;
for(int i=1;i<=n;i++){
mine=min(mine,b[i-1]-a[i]);
cvb=max(cvb,b[i]-a[i]-mine);
}
cout<<cvb<<endl;
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t=1;
//cin>>t;
while(t--){
solve();
}
}
