Multiples with small digits
Problem 303
Published on Saturday, 25th September 2010, 10:00 pm; Solved by 1817
For a positive integer n, define f(n) as the least positive multiple of n that, written in base 10, uses only digits 
2.
Thus f(2)=2, f(3)=12, f(7)=21, f(42)=210, f(89)=1121222.
Also, 
.
Find 
.