import java.util.Scanner;
class harry
{
	public static void main(String[] args) {
	Scanner sc = new Scanner(System.in);
	double n = sc.nextInt();
	Integer i = sc.nextInt();
	double k = sc.nextInt();

    double ans = (i-1) * Math.pow((i-1)/n, k);

    double sum = 0;
    for(int j = i; j < n; j++)
        sum = sum + Math.pow(j/n, k);

    ans = (ans + n + 1 - sum) / 2;

    System.out.println(ans);


	}
}