Strings

Accepts: 0
Submissions: 3
Time Limit: 2000/1000 MS (Java/Others)
Memory Limit: 131072/131072 K (Java/Others)
Problem Description
Cyy has m kinds of characters,numbered from 1 to m,and the cost of using an i-th character is i.He wants to use these characters to construct N nonempty strings.Every string can not be a prefix of another string.Now he wants to know what the minimum cost is.
Input
There are multiple test cases, no more than 1000 cases. For each case contains two integers n and m on a line.$(1\leq n\leq {10}^{9},2\leq m \leq {10}^{9})$
Output
For each test case,output minimum cost in a line.
Sample Input
1 2
3 2
5 2
1000 100000
Sample Output
1
7
17
10464