We increase $X$ by $1$ until we've found a solution. If we don't find one in $1000000$ iterations, then there is surely no such number and we output zero. What remains is to find a simple procedure to check if two integers $X$ and $Y$ consist of the same digits.

Separating an integer into digits can be done by repeatedly observing the last digit (remainder when dividing it by $10$) and dividing the number by $10$, while the number is not zero.

To check if $X$ and $Y$ consist of the same digits, we count how many times each of the $10$ digits appears in each number. If the counts match for all digits, the numbers consist of the same digits.