Simulation of a binomial problem in R

[homerjaysimpson]

I have 16 euros in my pocket and I play head or tails with p = 1/2. Every time I bet on heads. If the coin flip is head then I earn 0 and if is tails I lose 1 euro. What is the probability of hitting 18 times (consecutive or not) heads and to be left 3 euros in my pocket.

I tried to simulate this problem in R:

squid_bridge = function(a,n,p) {
  players = a
  while (position > 0 & position < n) {
    jump  =  sample(c(0,1),1,prob=c(1-p,p))
    position = position + jump
  }
  if (position == 0) 
    return(1) 
  else 
    return(0)
}   

n = 18
trials = 100000
a = 16
p = 1/2
set.seed(1)
simlist = replicate(trials, squid_bridge(a, n, p))

But it does seem to work.Any help?