Decrypt Agent code LARP NewAge

local key = {
  {"A","B","C","D","E"},
  {"F","G","H","I","K"},
  {"L","M","N","O","P"},
  {"Q","R","S","T","U"},
  {"V","W","X","Y","Z"},
}
local input = assert(io.open("crypted.txt", "r"), "Failed to open input 'crypted.txt' file")
local symbol, ch, text = true, nil, ""
while symbol do
  symbol = input:read(1)
  if tonumber(symbol) then
    if ch then
      text = text .. key[ch][tonumber(symbol)]
      ch = nil
    else
      ch = tonumber(symbol)
    end
  elseif symbol == string.char(32) then
    text = text .. " "
    ch = nil
  elseif symbol == string.char(10) or symbol == string.char(12) then
    text = text .. string.char(10)
    ch = nil
  end
end
print(text)
input:close()
local output = assert(io.open("result.txt", "w"), "Failed to open output file")
output:write(text)
output:close()