#CCC13S5. Factor Solitaire
Factor Solitaire
In the game of Factor Solitaire, you start with the number 1, and try to change it to some given target number n by repeatedly using the following operation. In each step, if c is your current number, you split it into two positive factors a, b of your choice such that c=a×b. You then add a to your current number c to get your new current number. Doing this costs you b points.
You continue doing this until your current number is n, and you try to achieve this at the cost of a minimum total number of points.
For example, here is one way to get to 15:
- start with 1
- change 1 to 1+1=2 — cost so far is 1
- change 2 to 2+1=3 — cost so far is 1+2
- change 3 to 3+3=6 — cost so far is 1+2+1
- change 6 to 6+6=12 — cost so far is 1+2+1+1
- change 12 to 12+3=15 — done, total cost is 1+2+1+1+4=9.
In fact, this is the minimum possible total cost to get 15. You want to compute the minimum total cost for other target end numbers.
Input Specification
The input consists of a single integer N≥1. In at least half of the cases N≤50000, in at least another quarter of the cases N≤500000, and in the remaining cases N≤5000000.
Output Specification
Compute the minimum cost that gets you to N.
Sample Input 1
15
Output for Sample Input 1
9
Sample Input 2
2013
Output for Sample Input 2
91
Explanation of Output for Sample Input 2
For example, start with 1, then get to 2, 4, 5, 10, 15, 30, 60, 61, 122, 244, 305, 610, 671, 1342, and then 2013.