/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] req = new int[n];
		int[] profit = new int[n];
		for(int i=0; i<n; i++){
			req[i] = sc.nextInt();
			profit[i] = sc.nextInt();
		}
 
		int minReq = 1;
		for(int i=n-1; i>=0; i--){
			int minEnter = minReq+req[i]-profit[i];
			minEnter = Math.max(minEnter, req[i]);
			minReq = minEnter;
		}
 
		System.out.println(minReq);
	}
}

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NQoyIDMKMyAwCjMgNQo1IDAKMSAy

5
2 3
3 0
3 5
5 0
1 2