#include <bits/stdc++.h> //Andrei Alexandru a.k.a Sho
using ll=long long;
using ld=long double;
int const INF=1000000005;
ll const LINF=1000000000000000005;
ll const mod=1000000007;
ld const PI=3.14159265359;
ll const MAX_N=3e5+5;
ld const EPS=0.00000001;
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#define f first
#define s second
#define pb push_back
#define mp make_pair
#define endl '\n'
#define sz(a) (int)a.size()
#define CODE_START ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
using namespace std;
ll n;
pair<ll,ll>a[500005];
int32_t main(){
CODE_START;
#ifdef LOCAL
ifstream cin("input.txt");
#endif
cin>>n;
for(ll i=1;i<=n;i++)
{
cin>>a[i].f>>a[i].s;
}
sort(a+1,a+n+1);
ll ans=0,sum=0,mn=a[1].f;
for(ll i=1;i<=n;i++)
{
sum+=a[i].s;
if(a[i].f+a[i].s>mn+sum){
sum=a[i].s;
mn=a[i].f;
}
ans=max(ans,sum-a[i].f+mn);
}
cout<<ans<<endl;
}
