n = int(input())    # 输入键值对的个数
dic = {}            # 创建一个空字典
for i in range(0,n):
    line = input().strip().split()
    key = int(line[0])
    value = int(line[1])
    dic[key] = dic.get(key,0) + value

for each in sorted(dic):
    print(each,dic[each])