from itertools import permutations

s = set()
dates = ['1720', '1727', '1747', '1828']
for d in permutations(dates, r=2):
  numbers = list(d[0]+d[1])
  s = s.union(set(permutations(numbers)))
n = len(s)

print(f'{n} chances sur 100000000')
print(f'{n/1000000}%')