#include<bits/stdc++.h>
#define fi first
#define se second
#define rep(a, b) for(int a = 0; a < (b); a++)
using namespace std;
typedef long long ll;
typedef vector<ll> vi;
typedef vector<ll> vl;
const int N=1e6+10;
pair<ll,ll> a[N];
ll sp[N];
void solve(){
int n;
cin>>n;
rep(i,n) cin>>a[i].fi>>a[i].se;
sort(a,a+n);
rep(i,n) sp[i+1]=sp[i]+a[i].se;
ll maxi=a[0].fi;
ll res=0;
rep(i,n){
maxi=max(maxi,-sp[i]+a[i].fi);
res=max(res,maxi+sp[i+1]-a[i].fi);
}
cout<<res<<"\n";
}
int main(){
ios_base::sync_with_stdio(0),cin.tie(0);
solve();
}
