require "ext"

local cpu = {
	r = {x = 1},
	isa = {
		addx = {
			nargs = 1,
			cycles = 2,
			f = function(self,v)
				self.r.x = self.r.x + tonumber(v)
			end
		},
		noop = {
			nargs = 0,
			cycles = 1,
			f = function(self) end
		}
	}
}

local strength_sum = 0
local cycle = 1
for line in io.lines() do
	local parts = {}
	for part in line:gmatch("(%S+)") do
		table.insert(parts,part)
	end
	local insn = table.remove(parts,1)
	local ins = cpu.isa[insn]
	assertf(ins, "No instruction %s in %s",insn,line)
	for i = cycle,cycle + ins.cycles - 1 do
		if (i - 20) % 40  == 0 then
			local strength = i * cpu.r.x
			strength_sum = strength_sum + strength
			break
		end
	end
	cycle = cycle + ins.cycles
	ins.f(cpu,table.unpack(parts))
end
print(strength_sum)