#include <bits/stdc++.h>
#define int long long
#define boost ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define file(s) freopen(s".in", "r", stdin); freopen(s".out", "w", stdout)
const int N=1e5+1;
const int inf=1e18;
const int mod=1e9+7;
using namespace std;
int n;
struct edge{
int ans,mx,mn,sum;
};
vector<edge>v1;
vector<pair<int,int> >v;
int pr[5*N];
signed main(){
boost;
int n;
cin>>n;
v.push_back({0,0});
for(int i=1;i<=n;i++){
int x,y;
cin>>x>>y;
v.push_back({x,y});
}
sort(v.begin(),v.end());
for(int i=1;i<=n;i++){
pr[i]=pr[i-1]+v[i].second;
}
int mx=0;
int ans=0;
for(int i=1;i<=n;i++){
mx=max(mx,v[i].first-pr[i-1]);
ans=max(ans,pr[i]-v[i].first+mx);
}
cout<<ans;
}
