def longestmountain(A):

peaks = {}

for i in range(1,len(A)-1):

if A[i] > A[i-1] and A[i] > A[i+1]:

peaks[i] = A[i]

left = 0

right = 0

val = 0

for i, j in peaks.items():

left = i-1

while left > 0 and A[left -1] < A[left]:

left = left - 1

right = i+1

while right < len(A)-1 and A[right] > A[right+1]:

right = right + 1

val = max(val, right-left+1)

return val

B=[10,15,16,9,4,3,11,1]

print(longestmountain(B))