#include <bits/stdc++.h>
using namespace std;
#define EPS 1e-9
#define ll long long
const int INF=1e9,mxN=5001;
const ll LINF=1e18,MOD=1e9+7;
#define fi first
#define se second
#define pii pair<int,int>
#define pll pair<long long,long long>
#define mid ((l+r)/2)
#define sz(a) (int((a).size()))
#define all(a) a.begin(),a.end()
#define endl "\n"
#define PRINT(x) cerr<<#x<<'='<<x<<endl;
#define pb push_back
#define PRINTvec(niz) { cerr<<#niz<<"="; for(auto _i:niz) cerr<<_i<<" "; cerr<<endl; }
#define PRINTpair(x) cerr<<#x<<"={"<<x.fi<<","<<x.se<<"}"<<endl;
void Solve(){
int N; cin>>N;
vector<pll> a(N+1);
for(int i=1;i<=N;i++) cin>>a[i].fi>>a[i].se;
sort(a.begin()+1,a.end());
ll res=0,mx=0;
for(int i=1;i<=N;i++){
mx=max(mx+a[i].se,a[i].fi+a[i].se);
res=max(res,mx-a[i].fi);
}
cout<<res<<endl;
}
int main(){
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int t; t=1;
//cin>>t;
while(t--){
Solve();
}
return 0;
}
