import sys

data=sys.stdin.readlines()[1:]

result={}
for line in data:
    i, v = line.strip().split()
    i = int(i)
    if i not in result:
        result[i]=int(v)
    else:
        result[i]+=int(v)
    
final=sorted(result.items(), key=lambda x:x[0])
for k, v in final:
    print(k, v)