import java.io.*;

import java.util.*;

public class convention2 {

public static void main(String[] args) throws IOException{

BufferedReader f= new BufferedReader(new FileReader("convention2.in"));

StringTokenizer st;

int N = Integer.parseInt(f.readLine());

Map<cow,Integer> senority = new HashMap<cow,Integer>();

ArrayList<cow> time = new ArrayList<cow>();

for(int i = 0; i < N ; i ++) {

st = new StringTokenizer(f.readLine());

cow thecow = new cow(Integer.parseInt(st.nextToken()),Integer.parseInt(st.nextToken()));

senority.put(thecow,i);

time.add(thecow);

thecow = null;

}

Collections.sort(time); // Looks a bit more stylish

//time.sort(null);

Comparator<cow> cowcompare = new Comparator<cow>() {

@Override

public int compare(cow arg0, cow arg1) {

// TODO Auto-generated method stub

return senority.get(arg0) - senority.get(arg1);

}

};

List<cow> theline = new ArrayList<cow>();

int c1; // Cache calculations

cow tc = new cow(-2,-2);

int mtime = -1,ctime,waittime;

ctime = 0;

cow c2;

int cows_eaten = 0;

int maxsenority;

//System.out.println(time);

while(cows_eaten < N || theline.size() > 0) {

if(theline.isEmpty()) {

tc = time.get(cows_eaten++);

ctime = tc.x;

}else {

tc = theline.remove(0);

waittime = ctime - tc.x;

if(waittime > mtime) {

mtime = waittime;

}

}

ctime = ctime + tc.y;

maxsenority = -1;

//cow nextcow = new cow(-1,-1); // Not guaranteed to have a conflicting time

int count = 0;

while(cows_eaten<N &&time.get(cows_eaten).x < ctime) {

theline.add(time.get(cows_eaten));

cows_eaten++;

count ++;

}

if(count>0) {theline.sort(cowcompare);}

}

//System.out.println(mtime);

PrintWriter pw = new PrintWriter(new FileWriter("convention2.out"));

pw.print(mtime);

pw.close();

}

}

class cow implements Comparable<cow>{

int x,y;

public cow(int i,int j) {

this.x = i;

this.y = j;

}

@Override

public int compareTo(cow arg0) {

// TODO Auto-generated method stub

return this.x - arg0.x;

}

@Override

public String toString() {

return "("+this.x+","+this.y+")";

}

@Override

public boolean equals(Object k) {

if(!(k instanceof cow)) {

return false;

}

cow c = (cow) k;

return (c.x == this.x) && (c.y == this.y);

}

}