Lk.waterman_function(a , k)
{
	#this program compute the probability of k-zero-run, P(Lk>=d), 
	# in a iid Bernoulli seq with P(1)=ps, 
	# where n is the length of seq., 
	# d is the length of Lk, and k is the num. of mismached.
	# output 3 values: est. of the prob, and its lower, upper bounds
	n <- length(a)
	d <- Lk.length(a, k)
	ps <- sum(a)/n
	s <- d - k
	EEW <- (n * (s/d - ps) * dbinom(s, d, ps)) * (-1)
	EEW <- exp(EEW)
	erro <- 7 * d * dbinom(s, d, ps) + (1 - pbinom(s, d, ps))
	upb <- EEW + erro
	lob <- EEW - erro
	bd <- c(EEW, upb, lob)
	bd <- 1 - bd
	if(bd[2] > 1)
		bd[2] <- 1
	if(bd[3] < 0)
		bd[3] <- 0
	bd[1]
}