import sys n = int(input()) temp = {} for i in range(n): #获取并处理数据 key,value = map(int,input().split(' ')) #根据字典特性进行简单判断 if key not in temp: temp[key] = value else: temp[key] += value #键值对按照升值排序 for i in sorted(temp): print(i,temp[i])