-- Get the printer on the left side
local printer = peripheral.wrap("left")

if not printer then
    print("No printer found on the left side!")
    return
end

-- Ask for the 7-number code
print("Enter a 7-digit code:")
local code = read()

-- Check that input is valid
if #code ~= 7 or not tonumber(code) then
    print("Invalid code! Must be 7 digits.")
    return
end

-- Extract first digit and map it
local firstDigit = tonumber(string.sub(code, 1, 1))
local prefix = ""

if firstDigit == 1 then
    prefix = "BUD"
elseif firstDigit == 2 then
    prefix = "LGW"
elseif firstDigit == 3 then
    prefix = "KBP"
else
    prefix = "???"
end

-- Combine with the rest of the code
local finalCode = prefix .. string.sub(code, 2)

-- Print to printer
printer.newPage()
printer.setCursorPos(1, 1)
printer.write(finalCode)
printer.endPage()

print("Code printed: " .. finalCode)