n=int(input())
dic={}#读完题快速想到字典
for n in range(n):
    line = input().split()
	#一定记得转换为int型
    key=int(line[0])
    value=int(line[1])
    if key not in dic:
        dic[key] = value
    else:
        dic[key] += value
for key in sorted(dic):
    print(key,dic[key])