UVa 10523 - Very Easy !!!

　　题目大意：给你一个公式，直接按照式子计算就可以了，要用到大数。

 import java.io.*;
 import java.util.*;
 import java.math.*;

 class Main
 {
     public static void main(String[] args)
     {
         Scanner sc = new Scanner(System.in);
         while (sc.hasNextInt())
         {
             int n = sc.nextInt();
             BigInteger a = BigInteger.valueOf(sc.nextInt());
             BigInteger sum = BigInteger.valueOf(0);
             BigInteger t = BigInteger.valueOf(1);
             for (int i = 1; i <= n; i++)
             {
                 t = t.multiply(a);
                 BigInteger tmp = t.multiply(BigInteger.valueOf(i));
                 sum = sum.add(tmp);
             }
             System.out.println(sum);
         }
     }
 }