Write a recursive C ++ function that returns the smallest even digit of a natural number transmitted as a parameter.
If the number does not contain any even digit, it will return -1.

Easy to do without recursion:

```
int cifminpar(int x)
{
    int mi = 9;
   while(x)
   {
       if(x % 10 % 2 == 0)
        mi = min(mi , x%10 );
       x /= 10;

   }
   if(mi == 9)
        return -1;
   else return mi;

}

```

How do I do that with recursion ?