while 1:

	n,m,p=list(map(int,input().split()))

	if n==0:break

	x=[eval(input()) for i in range(n)]

	print((100-p)*sum(x)/x[m-1] if x[m-1]!=0 else 0)
while 1:

	n,m,p=list(map(int,input().split()))

	if n==0:break

	x=[int(input()) for i in range(n)]

	print((100-p)*sum(x)/x[m-1] if x[m-1]!=0 else 0)
while 1:
    n, m, p = list(map(int, input().split()))
    if n == 0:
        break
    x = [eval(input()) for i in range(n)]
    print((100 - p) * sum(x) / x[m - 1] if x[m - 1] != 0 else 0)

while 1:
    n, m, p = list(map(int, input().split()))
    if n == 0:
        break
    x = [int(input()) for i in range(n)]
    print((100 - p) * sum(x) / x[m - 1] if x[m - 1] != 0 else 0)

-    x = [eval(input()) for i in range(n)] +    x = [int(input()) for i in range(n)]