python 解法

while True:
    try:
        n = int(input())
        res = {}
        for i in range(n):
            index, value = map(int,input().split())
            if index in res:
                res[index] += value
            else:
                res[index] = value
        for key in sorted(res):
            print('{} {}'.format(key,res[key]))
    except:
        break