599 B | 599 chars
import sys
from math import sqrt, pi, sin, factorial, ceil, floor
from decimal import Decimal
BLANK = " "
# inp = input
inp = lambda : sys.stdin.readline()[:-1].strip()
mii = lambda x = BLANK : [*map(int,inp().split(x))]
mfi = lambda x = BLANK : [*map(float,inp().split(x))]
ii = lambda : int(inp())
fi = lambda : float(inp())
p = print
def solve():
n, m, k = mii()
l = sorted(mii(), reverse=True)
ans = sum(l[:m])
for i in range(m, min(m + k, n)):
ans += l[i]
p(ans * 100 / sum(l))
if __name__ == "__main__":
tc = 1
for t in range(1, tc+1):
ret = solve()