题解 | #合并表记录#

import sys

n = int(input())
dic = {}
for i in range(n) :
    key, value = map(int, input().split())
    if key in dic :
        dic[key] += value
    else :
        dic[key] = value
# 根据key进行排序
answer = sorted(dic.items(), key = lambda x:x[0])
# answer 的结果为[(0, 3), (1, 2), (3, 4)]
# 遍历输出
for key in answer :
    print(str(key[0]) + ' ' + str(key[1]))