Write a recursive function to calculate the greatest common

denominator of two integers a and b $$ called gcdr$($a$,$b$).$ gcdr$($a$,$b$)$ is the largest common divisor.$gcdr(a,b)=\{\begin{array}{ccc}b& ifb\text{d}\text{i}\text{v}\text{i}\text{d}\text{e}\text{s}\text{a}\text{w}\text{i}\text{t}\text{h}no\text{r}\text{e}\text{m}\text{a}\text{i}\text{n}\text{d}\text{e}\text{r}& \\ gcd(b& \text{r}\text{e}\text{m}\text{a}\text{i}\text{n}\text{d}\text{e}\text{r}of\frac{a}{b})\text{o}\text{t}\text{h}\text{e}\text{r}\text{w}\text{i}\text{s}\text{e}& \end{array}$