n = int(input())
d = {}  # 使用一个字典存储合并后的键值对
for _ in range(n):
    i = input().split(" ")
    index, value = int(i[0]), int(i[1])
    d[index] = d.get(index, 0) + value  # 相同key的value值相加
for k in sorted(d.keys()):  # 遍历排序后的键,输出键值对
    print(f"{k} {d[k]}")