// Arup Guha
// 12/27/2018
// Solution to 2018 Dec Silver USACO Problem: Convention II

import java.util.*;
import java.io.*;

public class convention2 {
	
	public static int n;
	public static cow[] list;
	
	public static void main(String[] args) throws Exception {
		
		// Get basic info.
		BufferedReader stdin = new BufferedReader(new FileReader("convention2.in"));
		StringTokenizer tok = new StringTokenizer(stdin.readLine());
		n = Integer.parseInt(tok.nextToken());
		list = new cow[n];
		
		// Read in each cow and sort by time.
		for (int i=0; i<n; i++) {
			tok = new StringTokenizer(stdin.readLine());
			int s = Integer.parseInt(tok.nextToken());
			int t = Integer.parseInt(tok.nextToken());
			list[i] = new cow(s,t,i);
		}
		Arrays.sort(list);

		// Here is my list of cows who are waiting, by priority.
		PriorityQueue<cow> pq = new PriorityQueue<cow>(10, new Comparator<cow>() {
			public int compare(cow a, cow b) {
				return a.priority-b.priority;
			}
		});
		
		int curT = 0, res = 0;
		int curCow = 0;
		
		// Just run the simulation.
		while (curCow < n || pq.size() > 0) {
			
			if (curCow < n && list[curCow].start <= curT) {
				pq.offer(list[curCow++]);
			}
			
			// No one is waiting.
			else if (pq.size() == 0) {
				cow cur = list[curCow++];
				curT = cur.start + cur.time;
			}			
			
			// Cow is waiting in the queue.
			else {
				cow cur = pq.poll();
				res = Math.max(res, curT-cur.start);
				curT += cur.time;	
			}
		}
		
		// Solve and print out the result.
		PrintWriter out = new PrintWriter(new FileWriter("convention2.out"));
		out.println(res);
		out.close();		
		stdin.close();		
	}
}

class cow implements Comparable<cow> {
	
	public int start;
	public int time;
	public int priority;
	
	public cow(int s, int t, int p) {
		start = s;
		time = t;
		priority = p;
	}
	
	public int compareTo(cow other) {
		return this.start - other.start;
	}
	

}