d = [0,1,0,2,1,0,1,3,2,1,2,1]
#print(d)
n = len(d)
d_l = [0 for _ in range(n)] # max heights from left to right at the given position d[i]
max_l = 0
for i in range(n):
max_l = max(max_l, d[i])
d_l[i] = max_l
#print(d_l)
d_r = [0 for _ in range(n)] # max heights from right to left at the given position d[i]
max_r = 0
for i in range(n-1, -1, -1):
max_r = max(max_r, d[i])
d_r[i] = max_r
#print(d_r)
ans = 0
for i in range(n):
ans += min(d_l[i], d_r[i]) - d[i]
print(ans)
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