YA LALKA

class Vector:
    def __init__(self, x, y):
        self.x = x
        self.y = y

    def __neg__(self):
        return Vector(-self.x, -self.y)

    def __add__(self, other):
        return Vector(self.x + other.x, self.y + other.y)

    def __sub__(self, other):
        return Vector(self.x - other.x, self.y - other.y)

    def __mul__(self, k):
        return Vector(k * self.x, k * self.y)

    def __rmul__(self, k):
        return Vector(k * self.x, k * self.y)


def lenv(a, b):
    return ((a.x - b.x) ** 2 + (a.y - b.y) ** 2) ** 0.5
n, l, k = map(int,input().split())
if k > 0:
    holes = set(map(lambda x: int(x) - 1, input().split()))
else:
    holes = {}
fence = []
for i in range(n):
    x, y = map(int, input().split())
    fence.append(Vector(x, y))
ansM = 0
s = 0
for num in holes:
    nowl = l
    ansNow = 0
    pos = num
    flag = False
    s += lenv(fence[num], fence[(num + 1) % n])
    while nowl > 0 and not (flag and pos == num):
        if pos in holes:
            tmp = lenv(fence[pos], fence[(pos + 1) % n])
            if tmp <= nowl:
                ansNow += tmp
                nowl -= tmp
            else:
                ansNow += nowl
                nowl = 0
        else:
            nowl -= lenv(fence[pos], fence[(pos + 1) % n])
        pos += 1
        pos %= n
        flag = True
    #print(num, ansNow)
    ansM = max(ansM, ansNow)
    nowl = l
    ansNow = 0
    pos = num
    flag = False
    while nowl > 0 and not (flag and pos == num):
        if pos in holes:
            tmp = lenv(fence[pos], fence[(pos - 1) % n])
            if tmp <= nowl:
                ansNow += tmp
                nowl -= tmp
            else:
                ansNow += nowl
                nowl = 0
        else:
            nowl -= lenv(fence[pos], fence[(pos - 1) % n])
        pos -= 1
        pos %= n
        flag = True
    #print(num, ansNow)
    ansM = max(ansM, ansNow)
print('{:.6f}'.format(s - ansM))