UVa 10523

　　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);
        }
    }
}