x1 = int(input())
dic = {}
while True:
    try:
        line = input()
        x2 = line.split()
        key = int(x2[0])
        value = int(x2[1])
        if key in dic:
            dic[key] += value
        else:
            dic[key] = value

    except:
        break

for k,v in sorted(dic.items()):
    print(k,v)