Minimize Digitsum

You are given positive integers $N$ and $D$. You may perform operations of the following two types: - add $D$ to $N$, i.e. change $N$ to $N+D$ - change $N$ to $\mathop{\mathrm{digitsum}}(N)$ Here, $\mathop{\mathrm{digitsum}}(x)$ is the sum of decimal digits of $x$. For example, $\mathop{\mathrm{digitsum}}(123)=1+2+3=6$, $\mathop{\mathrm{digitsum}}(100)=1+0+0=1$, $\mathop{\mathrm{digitsum}}(365)=3