import sys

n = int(''.join(sys.stdin.readline().strip().split()))
d = {}
for i in range(n):
    x,y = sys.stdin.readline().strip().split()
    x,y = int(x),int(y)
    if x in d:
        d[x] += y
    else:
        d[x] = y
sorted_d = sorted(d.items())
for k,v in sorted_d:
    print(k,v ,end="\n")