I wish i can type chinese, but i'm at work...
here's my idea, not sure if it's correct strategy though.... there're 3 situations:
1. none of the 4 repeating ones fall in 1st position(million-th) & not zero (15*9*8*8*7)
2. the 4 repeating one start on 1st position (20*9*9*8*7)
3. the 4 repeating ones are zeros (15*1*9*8*7)
add the 3 up, then it goes my answer. hopefully you get the correct answer and let me know if i'm right :).
what grade is this question for?