Poj Solution 2665

http://poj.org/problem?id=2665

//* @author popop0p0popo
import java.util.*;
import java.io.*;

public class Main{
 public static void main(String[] args){
  Scanner scanner=new Scanner(new BufferedReader(new InputStreamReader(System.in)));
    int s,n,tn;
    while (true){
        s=scanner.nextInt();
        n=scanner.nextInt();
        if (s==0&&n==0){
            break;
        }
        tn=s+1;
        for (int i=0;i< n ;i++ ){
                   tn=tn+scanner.nextInt()-scanner.nextInt()-1;
        }
        System.out.println(tn);
    }
  }
}