题解 | #合并表记录#

import java.util.Scanner;
//用TreeMap就可以按照顺序输出键值对了
import java.util.TreeMap;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n=in.nextInt();
        
        TreeMap<Integer,Integer> mp=new TreeMap<>();

        for(int i=0;i<n;i++){
            int k=in.nextInt();
            int v=in.nextInt();
            if(mp.get(k)==null){
                mp.put(k,v);
            }else{
                mp.replace(k,mp.get(k)+v);
            }

        }
        for(Integer m:mp.keySet()){
            System.out.println(m+" "+mp.get(m));
        }


    }
}