n, m = map(int, input().split())
h = list(map(int, input().split()))
a = list(map(int, input().split()))
if n == m:
  nowmin = min(h)
  ans = 0
  for i in range(n):
    ans += (h[i] - nowmin) * a[i]
  print(ans)
  exit()
ans = 1000000000000000000000
for i in range(n - m):
  nowmin = 100000000
  for j in range(m):
    nowmin = min(nowmin, h[i + j])
  nowans = 0
  for j in range(m):
    nowans += (h[i + j] - nowmin) * a[i + j]
  ans = min(ans, nowans)
if ans == 1000000000000000000000:
  print(0)
else:
  print(ans)