local mfl, mce = math.floor, math.ceil

local ffi = require("ffi")
local C = ffi.C
ffi.cdef[[
long long atoll(const char*);
]]

local function lltonumber(str)
  return C.atoll(str)
end

local p, q, r, k = io.read():match("(%d+) (%d+) (%d+) (%d+)")
p, q, r = tonumber(p), tonumber(q), tonumber(r)
k = lltonumber(k)

local t = {{}}
for i = 1, 1000 do
  local v = i - 1
  local p1 = v % 10
  v = mfl(v / 10)
  local p2 = v % 10
  local p3 = mfl(v / 10)
  local d = (p1 + p2 + p3) % 10
  local dst = d * 100 + p3 * 10 + p2 + 1
  t[1][i] = dst
end
for i = 2, 100 do
  t[i] = {}
  for j = 1, 1000 do
    t[i][j] = t[i - 1][ t[i - 1][j] ]
  end
end
p = p % 10
q = q % 10
r = r % 10
if k == 1LL then
  print(p)
elseif k == 2LL then
  print(q)
elseif k == 3LL then
  print(r)
else
  k = k - 1LL
  local cur = p + q * 10 + r * 100 + 1
  for i = 1, 100 do
    if k % 2LL == 1LL then
      cur = t[i][cur]
    end
    k = k / 2LL
  end
  print((cur + 9) % 10)
end