import java.util.*; public class Main { public static void main(String[] args) { Scanner sc = new Scanner(System.in); int num = sc.nextInt(); HashMap<Integer,Integer> map=new HashMap<Integer,Integer>(); for (int i = 0;i<num;i++){ int key = sc.nextInt(); int value = sc.nextInt(); if(map.containsKey(key)){ map.put(key,map.get(key)+value); }else { map.put(key,value); } } Object[] arr = map.keySet().toArray(); Arrays.sort(arr); for (Object keys: arr ) { System.out.println(keys+" "+map.get(keys)); } } }