#include <bits/stdc++.h>
using namespace std;
#define int long long
#define fi first
#define se second
const int inf=1e18;
signed main()
{
int n;cin>>n;
pair<int,int>a[n+1];
for(int i=1;i<=n;i++)
{
cin>>a[i].fi>>a[i].se;
}
sort(a+1,a+n+1);
int b[n+1],pref[n+1]={0};
for(int i=1;i<=n;i++)
{
pref[i]=pref[i-1]+a[i].se;
b[i]=pref[i]-a[i].fi;
}
/*for(int i=1;i<=n;i++)cout<<a[i].fi<<" ";
cout<<endl;
for(int i=1;i<=n;i++)cout<<a[i].se<<" ";
cout<<endl;
for(int i=1;i<=n;i++)cout<<pref[i]<<" ";
cout<<endl;
for(int i=1;i<=n;i++)cout<<b[i]<<" ";
cout<<endl;*/
int maks=-inf,res=-inf;
for(int i=n;i>=1;i--)
{
maks=max(maks,b[i]);
res=max(res,maks+a[i].fi-pref[i-1]);
}
cout<<res<<endl;
return 0;
}
