Write the least positive integral value of `n` for which `((1+i)/(1-i))^n` is real.

Explanation

Given:
`((1+i)/(1-i))^(n)`is real

and we have to find value of n

so,

`((1+i)/(1-i))^(n)`= `(((1+i)(1+i))/((1-i)(1+i)))^(n)`

since `i^2=-1`

`((1+i)/(1-i))^(n)`= `((1+i^2+2i)/(1-i^2))^(n)`

`((1+i)/(1-i))^(n)`= `((1-1+2i)/(1+1))^(n)`

...