  We study the entanglement cost of the states in the contragredient space,
which consists of $(d-1)$ $d$-dimensional systems. The cost is always $\log_2
(d-1)$ ebits when the state is divided into bipartite $\C^d \otimes
(\C^d)^{d-2}$. Combined with the arguments in \cite{Matsumoto02}, additivity of
channel capacity of some quantum channels is also shown.
