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")

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