#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll MOD = 1e9+7;
const int N = 5e5+5;
ll a[N],p[N];
int n;
set<ll>s;
struct art{
ll A,B;
bool operator < (const art &rhs) const{
return A<rhs.A;
}
}d[N];
int main()
{
ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
cin>>n;
for(int i=1;i<=n;i++)cin>>d[i].A>>d[i].B;
sort(d+1,d+1+n);
s.insert(-d[1].A);
ll ans=-1;
for(int i=1;i<=n;i++){
ans=max(ans,d[i].B);
p[i]=p[i-1]+d[i].B;
}
for(int i=2;i<=n;i++){
ll val=*(s.begin());
ans=max(ans,p[i]-d[i].A-val);
s.insert(p[i-1]-d[i].A);
}
cout<<ans;
return 0;
}
