n = int(input()) dic = {} # idea: 动态建构字典 for i in range(n): line = input().split() key = int(line[0]) value = int(line[1]) dic[key] = dic.get(key, 0) + value # 累积key所对应的value for each in sorted(dic): # 最后的键值对按照升值排序 print(each, dic[each])