num = int(input())
ls = {}
for i in range(num):
    index,value =input().split(' ')
    index,value = int(index),int(value)
    if index not in ls:
        ls[index] = value
    else:
        ls[index] += value

for key,value in sorted(ls.items()):
    print(str(key) + ' '+str(value))