enum begin NOP = 0, LDA, STA, ADD, SUB, BRZ, JMP, STP end

local ops = {NOP = NOP, LDA = LDA, STA = STA, ADD = ADD,
             SUB = SUB, BRZ = BRZ, JMP = JMP, STP = STP}

local function load(prog)
    local mem = table.create(31, 1)
    for i = 0, 31 do mem[i] = 0 end
    local lines = prog:rstrip():split("\n")
    for i = 1, #lines do
        local line = lines[i]:strip()
        local split = line:split(" ")
        local instr = split[1]
        local addr = 0
        if #split == 2 then addr = tonumber(split[2]) end
        if ops[instr] then
            mem[i - 1] = ops[instr] * 32 + addr
        else
            local v = tonumber(instr)
            if v then mem[i - 1] = v end
        end
    end
    return mem
end

local function output(acc)
    print(acc)
end

local function interp(prog)
    local acc = 0
    local pc = 0
    local mem = load(prog)
    while true do
        local instr = mem[pc] >> 5
        local addr  = mem[pc] % 32
        pc += 1
        switch instr do
            case LDA:
                acc = mem[addr]
                break
            case STA:
                mem[addr] = acc
                break
            case ADD:
                acc += mem[addr]
                if acc > 255 then acc -= 256 end
                break
            case SUB:
                acc -= mem[addr]
                if acc < 0 then ac += 256 end
                break
            case BRZ:
                if acc == 0 then pc = addr end
                break
            case JMP:
                pc = addr
                break
        end
        if instr == STP or pc > 31 then break end
    end
    output(acc)
end

local progs = {
    [[
        LDA 3
        ADD 4
        STP
        2
        2
    ]],
    [[
        LDA 12
        ADD 10
        STA 12
        LDA 11
        SUB 13
        STA 11
        BRZ 8
        JMP 0
        LDA 12
        STP
        8
        7
        0
        1
    ]],
    [[
        LDA 14
        STA 15
        ADD 13
        STA 14
        LDA 15
        STA 13
        LDA 16
        SUB 17
        BRZ 11
        STA 16
        JMP 0
        LDA 14
        STP
        1
        1
        0
        8
        1
    ]],
    [[
        LDA 13
        ADD 15
        STA 5
        ADD 16
        STA 7
        NOP
        STA 14
        NOP
        BRZ 11
        STA 15
        JMP 0
        LDA 14
        STP
        LDA 0
        0
        28
        1



        6
        0
        2
        26
        5
        20
        3
        30
        1
        22
        4
        24
    ]],
    [[
        0
        0
        STP
        NOP
        LDA 3
        SUB 29
        BRZ 18
        LDA 3
        STA 29
        BRZ 14
        LDA 1
        ADD 31
        STA 1
        JMP 2
        LDA 0
        ADD 31
        STA 0
        JMP 2
        LDA 3
        STA 29
        LDA 0
        ADD 30
        ADD 3
        STA 0
        LDA 1
        ADD 30
        ADD 3
        STA 1
        JMP 2
        0
        1
        3
    ]]
}

for progs as prog do interp(prog) end