#include <bits/stdc++.h> //Andrei Alexandru a.k.a Sho10
#define ll long long
#define double long double
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#define all(a) (a).begin(), (a).end()
#define f first
#define s second
#define pb push_back
#define mp make_pair
#define pi pair
#define rc(s) return cout<<s,0
#define endl '\n'
#define mod (10*10*10*10*10*10*10*10*10+7)
#define PI 3.14159265359
#define MAXN 100005
#define INF 1000000005
#define LINF 1000000000000000005ll
#define CODE_START ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
using namespace std;
ll n,ans=0,sum=0,v[500005];
pair<ll,ll>a[500005];
int32_t main(){
CODE_START;
cin>>n;
for(ll i=1;i<=n;i++)
{
cin>>a[i].f>>a[i].s;
}
sort(a+1,a+n+1);
for(ll i=1;i<=n;i++)
{
a[i].s+=a[i-1].s;
}
ll mn=-a[1].f;
for(ll i=1;i<=n;i++)
{
ans=max(ans,a[i].s-mn-a[i].f);
if(i+1<=n){
mn=min(mn,a[i].s-a[i+1].f);
}
}
cout<<ans<<endl;
}
