题解 | #合并表记录#

import java.io.BufferedInputStream;
import java.util.Map;
import java.util.Scanner;
import java.util.TreeMap;


public class Main {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        Integer num = in.nextInt();
        Map<Integer, Integer> map = new TreeMap<>();
        for (int i = 0; i < num; i++) {
            if (i == 0) {
                map.put(in.nextInt(), in.nextInt());
            } else {
                Integer one = in.nextInt();
                Integer two = in.nextInt();

                if (map.containsKey(one)) {
                    map.put(one, map.get(one) + two);
                } else {
                    map.put(one, two);
                }
            }
        }
        for (Integer key : map.keySet()) {
            System.out.println(key + " " + map.get(key));
        }
    }
}