def solve(N, V, C):
    A = [0] * N
    A[0] = C[0]

    for i in range(1, N):
        A[i] = A[i - 1] + C[i]

    A = [A[i] / (i + 1) for i in range(N)]

    R = [(a, i) for i, a in enumerate(A)]
    R.sort()

    L = [0] * N
    L[N - 1] = 1

    v = V - N

    for i in range(N):
        if v < 0:
            break
        a, k = R[i]
        j, v = divmod(v, k + 1)
        L[k] += j

    T = [0] * N

    for i in range(N - 1, -1, -1):
        for j in range(i + 1):
            T[j] += L[i]

    print(sum(C[i] * T[i] for i in range(N)))


def main():
    N, V = list(map(int, input().split()))
    C = list(map(int, input().split()))
    solve(N, V, C)


if __name__ == '__main__':
    main()