import numpy as np

lines = sorted(int(x.strip()) for x in open("input.txt"))

lines.append(lines[-1]+3)
lines.insert(0, 0)
lines = np.array(lines)

diff = lines[1:] - lines[:-1]
unique, counts = np.unique(diff, return_counts=True)
cnt = dict(zip(unique, counts))

print(cnt)
print(cnt[1]*cnt[3])