#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());
vector<ll> pSum(n);
for (int i=0;i<n;i++){
pSum[i]=paintings[i].second + (i>0 ? pSum[i-1] : 0);
}
ll ans=0;
for (int i=0;i<n;i++){
for (int j=0;j<=i;j++){
ll maxx=paintings[i].first;
ll minn=paintings[j].first;
ll sum;
if (j==0) sum=pSum[i];
else sum=pSum[i]-pSum[j-1];
ll wyn=compute(sum,minn,maxx);
//cout<<"min: "<<minn<<" max: "<<maxx<<" sum: "<<sum<<" wynik: "<<wyn<<"\n";
ans=max(ans,wyn);
}
}
cout<<ans;
return 0;
}
