Help:=proc(): print(`Drunk2(n), Polya(n,K) `):end:

#random walk of length n
Drunk2:=proc(n) local w,i,ra,pt,pt1,die1:
pt:=[0,0]:
w:=[]:
ra:=rand(1..4):

 for i from 1 to n do
  die1:=ra():
    if die1=1 then
      pt1:=[pt[1]+1,pt[2]]:

  elif die1=2 then
      pt1:=[pt[1]-1,pt[2]]:
  elif die1=3 then
      pt1:=[pt[1],pt[2]+1]:
   else 
      pt1:=[pt[1],pt[2]-1]:
  fi:
 
  w:=[op(w),pt1]:

  pt:=pt1:
 od:
w:
end:


#Polya(n,K): out of K randomly-generated
#2-dim walks how many revisit the origin
Polya:=proc(n,K) local co,i:
co:=0:

for i from 1 to K do
  if member([0,0], Drunk2(n)) then
    co:=co+1:
  fi:
od:

co/K:
end: