Computercraft Money Booth Timer

term.clear()
term.setCursorPos(1,1)
check = 1

while check == 1 do
    term.setTextColor(colors.yellow)
    print("\"Money\" Booth V1")
    print("Please enter duration in seconds:")
    input = tonumber(read())
    if tonumber(input) == nil then
        term.setTextColor(colors.red)
        print("Invalid Selection! Please try again.")
    else
        check = 0
    end
end

print("Timer set to: " .. input .. " seconds!")
print("Press \"enter\" to begin!")
read()

rs.setBundledOutput("back", colors.white)
while input > 0 do
    term.setTextColor(colors.yellow)
    term.clear()
    term.setCursorPos(1,1)
    print("\"Money\" Booth V1")
    print("There are " .. input .. " seconds remaining!")
    sleep(1)
    input = input - 1
end
rs.setBundledOutput("back", 0)
term.clear()
term.setCursorPos(1,1)
print("Times Up!")