import sys
readline=sys.stdin.readline
import numpy as np

N,L=map(int,readline().split())
L*=60
S=[]
for s in readline().split():
    mm,ss=map(int,s.split(":"))
    S.append(mm*60+ss)
ans=0
S_sum=sum(S)
if L>=S_sum:
    ans=N
else:
    fact=np.zeros(51)
    fact[0]=1.0
    for i in range(1,51):
        fact[i]=fact[i-1]*i
    dp=np.zeros((N+1,18001))
    dp[0,0]=1/fact[N]
    for s in S:
        dp[1:,s:]+=dp[:-1,:-s]
    for s in S:
        for i in range(1,N+1):
            dp[i,s:]-=dp[i-1,:-s]
        for i in range(N):
            for j in range(L):
                ans+=fact[i]*dp[i,j]*fact[N-i-1]
        for i in range(N,0,-1):
            dp[i,s:]+=dp[i-1,:-s]
print(ans)