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")