dic = {}
n = int(input())
while True:
    try:
        line = input()
        tmp = line.split()
        index = int(tmp[0])
        value = int(tmp[1])
        if index in dic:
            dic[index] += value
        else:
            dic[index] = value
    except:
        break
for k, v in sorted(dic.items()):
    print(f'{k} {v}')