#include<bits/stdc++.h>
#define ll long long
#define int long long
#define maxn 500005
#define fi first
#define se second
#define sti string
using namespace std;
pair<int,int> a[maxn];
int n;
ll pre[maxn];
signed main ()
{
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
cin>>n;
for(int i=1;i<=n;i++) cin>>a[i].fi>>a[i].se;
sort(a+1,a+n+1);
for(int i=1;i<=n;i++) pre[i]=pre[i-1]+a[i].se;
ll ans=0;
ll Min=4e18;
for(int r=1;r<=n;r++){
Min=min(Min,pre[r-1]-a[r].fi);
ans=max(ans,(pre[r]-a[r].fi)-Min);
}
cout<<ans;
return 0;
}
