import sys
from collections import defaultdict

fname = sys.argv[1]
with open(fname) as fin:
    data = defaultdict(list)  
    for line in fin:
        x,y = line.split()
        data[int(x)].append(float(y))

for k,v in sorted(data.items()):
    for i,elem in enumerate(v):
        print i,elem
    print
    print