# import sys

# for line in sys.stdin:
#     a = line.split()
#     print(int(a[0]) + int(a[1]))
n=int(input())
dict1={}
list1=[]
for i in range(n):
    list1=input().split()
    key1=int(list1[0])
    value1=int(list1[1])
    dict1[key1]=int(dict1.get(key1,0))+int(value1) #dict1.get(key1,0):表示如果键不在字典中，则返回默认值0
# print(dict1)
dict2=sorted(dict1)
# print(dict2,type(dict2))
for i in dict2:
    print(i,dict1[i])