import java.util.Scanner;
import java.math.BigInteger;
public class Main {
public static void main(String[] args) {
Scanner cin = new Scanner(System.in);
while (cin.hasNext()) {
int n = cin.nextInt();
BigInteger a = cin.nextBigInteger();
BigInteger power = a;
BigInteger sum = BigInteger.ZERO;
for (int i = 1; i <= n; i++) {
sum = sum.add(BigInteger.valueOf(i).multiply(power));
power = power.multiply(a);
}
System.out.println(sum.toString());
}
cin.close();
}
}