Find the smallest positive integer whose last digit is "6" such that moving
the "6" to the beginning of the number increases its value by a factor of 4.
For example, the number 1236 would be transformed to 6123, which is more
than four times as large, while 3126 becomes 6312, which is less than
four times as large. You are to find a number which is transformed to one
exactly four times as large.