AP ICET 11 Sep 2020 Shift 1 Paper

Let $\mathit{x}\mathrm{and}\mathit{y}$ be two positive integers with $\mathit{x}>\mathit{y}$ and when $\mathit{x}$ is divided by $\mathit{y}$, the remainder obtained is $\mathit{d}$. When $\mathit{y}$ is divided by $\mathit{d}$ leaves a remainder $\mathit{f}$ and when d is divided by $\mathit{f}$ leaves zero as remainder, then the greatest common divisor of $\mathit{x}\mathrm{and}\mathit{y}$ is