#include <iostream>
#include <algorithm>
#include <vector>
#include <map>
using namespace std;
const long long N = 200010;
vector<pair<long long,long long>> v1;
int main() {
long long n;
cin>>n;
for(long long i=1;i<=n;i++){
long long x,y;
cin>>x>>y;
v1.push_back(make_pair(x,y));
}
sort(v1.begin(),v1.end());
long long tempmin = -1*v1[0].first;
long long tempmax = v1[0].second-tempmin-v1[0].first;
for(long long i=1;i<n;i++){
v1[i].second+=v1[i-1].second;
tempmin = min(tempmin, v1[i-1].second-v1[i].first);
tempmax = max(tempmax,v1[i].second-v1[i].first -tempmin);
}
cout<<tempmax<<endl;
}
