Clearly $R=1$, and from the hundreds column, $M=0$ or 9. Since $H+G=9+O$ or $10+O$, it is easy to see that $O$ can be at most 7, in which case $H$ and $G$ must be 8 and 9, so $M=0$. But because of the tens column, we must have $S+T \geq 10$, and in fact since $D$ cannot be 0 or $1, S+T \geq 12$, which is impossible given the remaining choices. Therefore, $O$ is at most 6. Suppose $O=6$ and $M=9$. Then we must have $H$ and $G$ be 7 and 8. With the remaining digits $0,2,3,4$, and 5, we must have in the ones column that $T$ and $S$ are 2 and 3, which leaves no possibility for $N$. If instead $M=0$, then $H$ and $G$ are 7 and 9. Since again $S+T \geq 12$ and $N=T+1$, the only possibility is $S=8, T=4$, and $N=5$, giving $R O U N D=16352=7004+9348=9004+7348$.