import java.util.*;
import java.io.*;
public class art {
public static void main(String[] args) throws IOException{
BufferedReader f = new BufferedReader(new InputStreamReader(System.in));
PrintWriter out = new PrintWriter(new PrintStream(System.out));
int n=Integer.parseInt(f.readLine());
long ans=0;
pair[]arr=new pair[n];
for(int i=0;i<n;i++){
StringTokenizer st=new StringTokenizer(f.readLine());
long a=Long.parseLong(st.nextToken());
long b=Long.parseLong(st.nextToken());
ans=Math.max(ans,b);
arr[i]=new pair(a,b);
}
Arrays.sort(arr);
long best=0;
long pfx=0;
long lastpfx=0;
for(int i=0;i<n;i++){
pfx+=arr[i].val;
ans=Math.max(pfx-arr[i].size+best,ans);
best=Math.max(best,-lastpfx+arr[i].size);
lastpfx=pfx;
}
System.out.print(ans);
f.close();
out.close();
}
}class pair implements Comparable <pair>{
Long size;
Long val;
public int compareTo(pair other){
if(size>other.size)return 1;
return -1;
}
pair(long a, long b)
{
size=a;
val=b;
}
}
