import sys
from functools import reduce

from typing import List, Tuple


def int1(x: str, /): return int(x) - 1


def input(): return sys.stdin.readline().rstrip('\n')


def dbg(*args, **kwargs):
    print(*(repr(arg) for arg in args), *(f'{k}: {repr(v)}' for k, v in kwargs.items()), sep='; ', file=sys.stderr)


def t(s):
    return reduce(lambda a, b: 60 * a + b, map(int, s.split(':')), 0)


def main():
    n, l = map(int, input().split())
    l *= 60
    *s, = map(t, input().split())
    if sum(s) <= l:
        return n

    d = [[0] * l for _ in range(n + 1)]
    d[0][0] = 1
    for i in range(n):
        for j in range(n, 0, -1):
            for k in range(s[i], l):
                d[j][k] += d[j - 1][k - s[i]]

    ans = 0
    mul = 1
    for i in range(n):
        ans += sum(d[i]) / mul
        mul *= (n - i)
        mul //= i + 1

    return ans


def _start():
    ret = main()

    if ret is not None:
        if isinstance(ret, List) or isinstance(ret, Tuple):
            print(*ret)
        else:
            print(ret)


if __name__ == '__main__':
    _start()