#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vii;
typedef pair<int,int> pi;
typedef vector<pi> pii;
typedef tuple<int,int,int> ti;
typedef vector<ll> li;
typedef vector<li> lii;
#define REP(i,a,b) for(int i=a;i<b;i++)
#define F first
#define S second
#define PB push_back
#define LSOne(s) ((s)&(-s))
#define all(x) (x).begin(),(x).end()
ll INF=1000000000000000010;
int inf=1e9+10;
ll M=1e9+7;
int main(){
ios::sync_with_stdio(0);
cin.tie(0);
int n;cin>>n;
vector<pair<ll,ll>> a(n);
REP(i,0,n)cin>>a[i].F>>a[i].S;
sort(all(a));
ll ans=0,k=a[0].F;
REP(i,0,n)ans=max(ans,a[i].S);
REP(i,1,n)a[i].S+=a[i-1].S;
REP(i,1,n){
ans=max(ans,a[i].S-a[i].F+k);
k=max(k,a[i].F-a[i-1].S);
}
cout<<ans;
}
