#include<bits/stdc++.h>
#define endl '\n'
#define fi first
#define se second
using namespace std;
const int MAXN=5e5+5;
int n;
pair<long long,int> a[MAXN];
long long d[MAXN];
int suffMax[MAXN];
int main()
{
ios::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
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++) d[i]=d[i-1]+a[i].se;
for(int i=1;i<=n;i++) d[i]-=a[i].fi;
suffMax[n]=n;
for(int i=n-1;i>=1;i--)
{
suffMax[i]=suffMax[i+1];
if(d[i]>d[suffMax[i+1]]) suffMax[i]=i;
}
long long ans=a[n].se;
for(int i=1;i<n;i++)
{
long long cur=a[i].se;
cur=max(cur, d[suffMax[i+1]]-d[i-1]-a[i-1].fi+a[i].fi);
ans=max(ans, cur);
}
cout<<ans<<endl;
return 0;
}
