local ior = io.input()
local n, m, k = ior:read("*n", "*n", "*n")
local matrix_list = {}

local function make_matrix()
  local tmp = {}
  for i = 1, n * n do tmp[i] = 0 end
  return tmp
end

for i = 1, m do
  local a, b, c = ior:read("*n", "*n", "*n")
  if(matrix_list[c] == nil) then
    matrix_list[c] = make_matrix()
  end
  matrix_list[c][(a - 1) * n + b] = 1
  matrix_list[c][(b - 1) * n + a] = 1
end

local vec = {}
for i = 1, n do vec[i] = 1 end
local mmi = math.min
for i_k = 1, k do
  local mat = matrix_list[ior:read("*n")]
  local ret_vec = {}
  for i = 1, n do ret_vec[i] = 0 end
  for i = 1, n do
    for j = 1, n do
      ret_vec[i] = ret_vec[i] + mat[(i - 1) * n + j] * vec[j]
    end
    ret_vec[i] = mmi(1, ret_vec[i])
  end
  vec = ret_vec
end
local cnt = 0
for i = 1, n do
  if(0 < vec[i]) then cnt = cnt + 1 end
end
print(cnt)
local fst = true
for i = 1, n do
  if(0 < vec[i]) then
    if(fst) then
      fst = false
    else
      io.write(" ")
    end
    io.write(i)
  end
end
io.write("\n")