#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx,avx2,fma")
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define OYY 100000000000005
#define mod 1000000007
#define faster ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define FOR for(int i=1;i<=n;i++)
#define mid (start+end)/2
#define lim 300005
#define fi first
#define se second
vector<pair<int,int>> dizi;
int32_t main(){
faster
int n;cin>>n;
dizi.push_back({-LLONG_MAX,-LLONG_MAX});
FOR{
int x,y;cin>>x>>y;
dizi.push_back({x,y});
}
sort(dizi.begin(),dizi.end());
int cev=-LLONG_MAX,sum=0,mini=0;
FOR{
mini=max(mini,dizi[i].fi-sum);
sum+=dizi[i].se;
cev=max(cev,sum-(dizi[i].fi-mini));
}
cout<<cev<<endl;
return 0;
}
