let rng = System.Random()
let add x y = x + y
let wall d n =
if d = 1 || n = 1 || d = 20
|| n = 20 then "#"
else "."
let zebra a b =
if a = b then "W"
else "B"
let rand row col =
match rng.Next() % 5 with
| 0 -> "."
| 1 -> "$"
| 2 -> "&"
| 3 -> "@"
| 4 -> ")"
//let z=add 9753 8642
//printf "%d" z
for i in 1..20 do
for j in 1..20 do
printf "%s" (wall i j)
printfn ""