P, Q, R, K = gets.split.map(&:to_i)

dp = Array.new(2000, 0)
dp[1] = P % 10
dp[2] = Q % 10
dp[3] = R % 10

4.upto(1500) do |i|
  dp[i] = (dp[i - 1] + dp[i - 2] + dp[i - 3]) % 10
end

intr = (0...1980).select { |i| dp[i] == P % 10 && dp[i + 1] == Q % 10 && dp[i + 2] == R % 10 }
k = intr[1] - intr[0]
r = K % k
puts dp[r]