N = int(1e4 + 10)

hash = [0] * N

def is_prime(x):
    if x < 2:
        return False

    for i in range(2,int(x ** 0.5) + 1):
        if x % i == 0:
            return False
    return True

def find(x): # 一个函数完成两个功能，x所在下标和查找的时间
    start = x % m_size
    for i in range(m_size):
        k = (start + i * i) % m_size
        if hash[k] == x or hash[k] == 0:
            return (k,i + 1)
    return (-1,m_size + 1)

m_size,n,m = map(int,input().split())

while not is_prime(m_size):
    m_size += 1

for x in map(int,input().split()):
    t = find(x)
    if t[0] == -1:
        print(f'{x} cannot be inserted.')
    else:
        hash[t[0]] = x

res = 0
for x in map(int,input().split()):
    res += find(x)[1]

print(f'{res / m:.1f}')