First Person to Say 50

You and an interviewer play a counting game. Starting from a running total of $0$, the players alternate turns. On each turn a player says a new total that is between $1$ and $10$ larger than the current total (inclusive), so after a total of $4$ the next player may say any number from $5$ to $14$. A player who says a number of $50$ or higher loses.

You move first and play optimally. Which number should you say on your first turn to guarantee a win?