local read = setmetatable({}, {__index = function(t, k) local a = {} for i=1,#k do table.insert(a, '*'..string.sub(k, i, i)) end local r = io.read local u = table.unpack or unpack return function() return r(u(a)) end end})
read.N = function(N) local t={} for i=1,N do t[i]=read.n() end return t end
string.totable = function(s) local t={} local u=string.sub for i=1,#s do t[i] = u(s, i, i) end return t end
string.split = function(s) local t={} for w in string.gmatch(s, "[^%s]+") do table.insert(t, w) end return (table.unpack or unpack)(t) end
local function array(dimensi0n, default_val) assert(type(default_val) ~= 'table') local n=dimensi0n local m={}if default_val~=nil then m[1]={__index=function()return default_val end}end for i=2,n do m[i]={__index=function(p, k)local c=setmetatable({},m[i-1])rawset(p,k,c)return c end}end return setmetatable({},m[n])end
local function tostringxx(o, depth) depth = depth or 0 if depth > 10 then return "<too deep!>" end if o == _G then return "<_G>" end local indent0 = (" "):rep((depth) * 2) local indent1 = (" "):rep((depth+1) * 2) local indent2= (" "):rep((depth+2) * 2) if type(o) == 'table' then local keys = {} local types = {} for k in pairs(o) do types[type(k)] = true table.insert(keys, k) end local types_count = 0 local lasttype for k in pairs(types) do types_count = types_count + 1 lasttype = k end if types_count == 1 and (lasttype == 'string' or lasttype == 'number') then table.sort(keys) end local inside = {} for i=1,#keys do local k = keys[i] local v = o[k] if type(k) == 'string' then k = string.format('%q', k) end table.insert(inside, indent1 .. '['..tostring(k)..'] = ' .. tostringxx(v, depth + 1)) end return '{\n' .. table.concat(inside, ',\n') .. '\n' .. indent0 .. '}' else if type(o) == 'string' then o = string.format('%q', o) end return tostring(o) end end
local function richtraceback() local x = 2 while true do local info = debug.getinfo(x) if not info then break end local fname = '<' .. info.short_src .. ":" .. info.linedefined .. ">" if info.name then fname = info.name end print(info.short_src .. ":" .. info.currentline .. ": in " .. ("%q"):format(fname)) print(" LOCALS:") local p = 1 while true do local name, val = debug.getlocal(x,p) if not name then break end print(" " .. name .. ": " .. tostringxx(val, 3)) p = p + 1 end print(" UPVALUES:") for p=1,info.nups do local name, val = debug.getupvalue(info.func,p) if not name then break end print(" " .. name .. ": " .. tostringxx(val, 3)) end x = x + 1 end end
local function myassert(b) if not b then richtraceback() error("assertion failed") end end 
--
local max = math.max

local R, C, K = read.nnn()
local item = array(1,0)
for i=1,K do
    local r,c,v = read.nnn()
    item[r*C + c] = v
end

local target1
local target2
local function chmax1(g,val)
    target1[g] = max(target1[g], val)
end
local function chmax2(g,val)
    target2[g] = max(target2[g], val)
end
local dp = array(2,0)

dp[1][0] = 0
dp[1][1] = item[1*C+1]
for r=1,R do
    for c=1,C do
        target1 = dp[c]
        target2 = dp[c+1]
        local rval = item[r*C+c+1]
        local dval = item[(r+1)*C+c]
        local cur0 = target1[0]
        local cur1 = target1[1]
        local cur2 = target1[2]
        local cur3 = target1[3]
        target1[0] = 0
        target1[1] = 0
        target1[2] = 0
        target1[3] = 0
        chmax1(1,cur0+dval)
        chmax1(0,cur0)
        chmax1(1,cur1+dval)
        chmax1(0,cur1)
        chmax1(1,cur2+dval)
        chmax1(0,cur2)
        chmax1(1,cur3+dval)
        chmax1(0,cur3)
        chmax2(0+1,cur0+rval)
        chmax2(0,cur0)
        chmax2(1+1,cur1+rval)
        chmax2(1,cur1)
        chmax2(2+1,cur2+rval)
        chmax2(2,cur2)
        chmax2(3+1,cur3+rval)
        chmax2(3,cur3)
    end
end
print(max(dp[C][0],dp[C][1],dp[C][2],dp[C][3]))

Measured memory_bytes: 16580