from math import log
n = int(input())
b = int(input())
a = list(map(float, input().split())) 
def bibun(x):
    return print(sum([i* x**(i-1) for i in a]))
def sekib(x):
    c = []
    for j in a:
        if j == -1:
            c.append(log(b))
        else:
            c.append( 1/(j+1) * b**(j+1) )
    return print(sum(c))

def main(x):
    bibun(x)
    sekib(x)
    
if __name__ == "__main__":
    main(b)