#include<iostream>
#include<algorithm>
using namespace std;
pair<int,int>cow[50005];
int main()
{
int n,i,s,w,ans=-2e9,sum=0;
scanf("%d",&n);
for(i=0;i<n;i++){
scanf("%d%d",&w,&s);
cow[i]={w+s,w};
}
sort(cow,cow+n);
for(i=0;i<n;i++)s=cow[i].first-cow[i].second,w=cow[i].second,ans=max(ans,sum-s),sum+=w;
printf("%d\n",ans);
return 0;
}