Buggy python submission (verdict: Runtime Error):
from collections import deque
n=int(input())
a=list(map(int,input().split()))
A=[a[0]+a[0]<a[1]-a[0]>a[1]]+a+[a[-1]+a[-1]<a[-2]-a[-1]>a[-2]]
valley=0
peak=1
dp=deque()
for i in range(1,n+1):
  if A[i-1]<A[i]>A[i+1]:
    dp.append((i-1,peak))
  elif A[i-1]>A[i]<A[i+1]:
    dp.append((i-1,valley))
l,lf=dp.popleft()
r,rf=dp.popleft()
if lf == peak:
  ans=a[0]
else:
  ans=a[0]*(r+1)
for i in range(1,n-1):
  if r == i:
    t,tf=r,rf
    r,rf=dp.popleft()
    if tf == valley:
      ans+=a[i]*(i-l+1)*(r-i+1)
    else:
      ans+=a[i]
    l,lf=t,tf
  else:
    if lf == valley:
      ans+=a[i]*(r-i+1)
    else:
      ans+=a[i]*(i-l+1)
if rf == valley:
  ans+=a[-1]*(n-l)
else:
  ans+=a[-1]
print(ans)


Fixed submission:
class BinaryIndexedTree:
    # http://hos.ac/slides/20140319_bit.pdf
    def __init__(self, size):
        """
        :param int size:
        """
        self.bit = [0 for _ in range(size)]
        self.size = size

    def add(self, i, w):
        """
        i番目にwを加える
        :param int i:
        :param int w:
        :return:
        """
        x = i + 1
        while x <= self.size:
            self.bit[x - 1] += w
            x += x & -x
        return

    def sum(self, i):
        """
        [0,i]の合計
        :param int i:
        :return:
        """
        res = 0
        x = i + 1
        while x > 0:
            res += self.bit[x - 1]
            x -= x & -x
        return res

    def search(self, x):
        """
        二分探索。和がx以上となる最小のインデックス(>= 1)を返す
        :param int x:
        :return :
        """
        i = 0
        s = 0
        step = 1 << self.size.bit_length()
        while step:
            if i + step <= self.size and s + self.bit[i + step - 1] < x:
                print(self.bit[i + step - 1], i, step)
                i += step
                s += self.bit[i - 1]
            step >>= 1
        return i

    def __len__(self):
        return self.size
from collections import defaultdict
n=int(input())
a=list(map(int,input().split()))
d=defaultdict(int)
for i in range(n):
  d[a[i]]=i+1
Bit = BinaryIndexedTree(n+1)
ans=0
for i in range(n):
  j=i+1
  i=d[j]
  x=Bit.sum(i)
  ok=i
  ng=-1
  while ok - ng > 1:
    mid=(ok+ng)//2
    if Bit.sum(mid)==x:
      ok=mid
    else:
      ng=mid
  l=ok+1
  ok=i
  ng=n+1
  while ng - ok > 1:
    mid=(ok+ng)//2
    if Bit.sum(mid)==x:
      ok=mid
    else:
      ng=mid
  r=ok
  ans+=j*(i-l+1)*(r-i+1)
  Bit.add(i,1)
print(ans)

Buggy python submission (verdict: Runtime Error):
from collections import deque
n=int(input())
a=list(map(int,input().split()))
A=[a[0]+a[0]<a[1]-a[0]>a[1]]+a+[a[-1]+a[-1]<a[-2]-a[-1]>a[-2]]
valley=0
peak=1
dp=deque()
for i in range(1,n+1):
  if A[i-1]<A[i]>A[i+1]:
    dp.append((i-1,peak))
  elif A[i-1]>A[i]<A[i+1]:
    dp.append((i-1,valley))
l,lf=dp.popleft()
r,rf=dp.popleft()
if lf == peak:
  ans=a[0]
else:
  ans=a[0]*(r+1)
print(ans)
for i in range(1,n-1):
  if r == i:
    t,tf=r,rf
    r,rf=dp.popleft()
    if tf == valley:
      ans+=a[i]*(i-l+1)*(r-i+1)
    else:
      ans+=a[i]
    l,lf=t,tf
  else:
    if lf == valley:
      ans+=a[i]*(r-i+1)
    else:
      ans+=a[i]*(i-l+1)
if rf == valley:
  ans+=a[-1]*(n-l)
else:
  ans+=a[-1]
print(ans)


Fixed submission:
class BinaryIndexedTree:
    # http://hos.ac/slides/20140319_bit.pdf
    def __init__(self, size):
        """
        :param int size:
        """
        self.bit = [0 for _ in range(size)]
        self.size = size

    def add(self, i, w):
        """
        i番目にwを加える
        :param int i:
        :param int w:
        :return:
        """
        x = i + 1
        while x <= self.size:
            self.bit[x - 1] += w
            x += x & -x
        return

    def sum(self, i):
        """
        [0,i]の合計
        :param int i:
        :return:
        """
        res = 0
        x = i + 1
        while x > 0:
            res += self.bit[x - 1]
            x -= x & -x
        return res

    def search(self, x):
        """
        二分探索。和がx以上となる最小のインデックス(>= 1)を返す
        :param int x:
        :return :
        """
        i = 0
        s = 0
        step = 1 << self.size.bit_length()
        while step:
            if i + step <= self.size and s + self.bit[i + step - 1] < x:
                print(self.bit[i + step - 1], i, step)
                i += step
                s += self.bit[i - 1]
            step >>= 1
        return i

    def __len__(self):
        return self.size
from collections import defaultdict
n=int(input())
a=list(map(int,input().split()))
d=defaultdict(int)
for i in range(n):
  d[a[i]]=i+1
Bit = BinaryIndexedTree(n+1)
ans=0
for i in range(n):
  j=i+1
  i=d[j]
  x=Bit.sum(i)
  ok=i
  ng=-1
  while ok - ng > 1:
    mid=(ok+ng)//2
    if Bit.sum(mid)==x:
      ok=mid
    else:
      ng=mid
  l=ok+1
  ok=i
  ng=n+1
  while ng - ok > 1:
    mid=(ok+ng)//2
    if Bit.sum(mid)==x:
      ok=mid
    else:
      ng=mid
  r=ok
  ans+=j*(i-l+1)*(r-i+1)
  Bit.add(i,1)
print(ans)

Buggy python submission (verdict: Runtime Error):
from collections import deque
n=int(input())
a=list(map(int,input().split()))
A=[a[0]+a[0]<a[1]-a[0]>a[1]]+a+[a[-1]+a[-1]<a[-2]-a[-1]>a[-2]]
valley=0
peak=1
dp=deque()
for i in range(1,n+1):
  if A[i-1]<A[i]>A[i+1]:
    dp.append((i-1,peak))
  elif A[i-1]>A[i]<A[i+1]:
    dp.append((i-1,valley))
l,lf=dp.popleft()
r,rf=dp.popleft()
if lf == peak:
  ans=a[0]
else:
  ans=a[0]*(r+1)
for i in range(1,n-1):
  if r == i:
    t,tf=r,rf
    r,rf=dp.popleft()
    if rf == valley:
      ans+=a[i]*(i-l+1)*(r-i+1)
    else:
      ans+=a[i]
  	l,lf=t,tf
  else:
    if lf == valley:
      ans+=a[i]*(r-i+1)
    else:
      ans+=a[i]*(i-l+1)
print(ans)

Fixed submission:
class BinaryIndexedTree:
    # http://hos.ac/slides/20140319_bit.pdf
    def __init__(self, size):
        """
        :param int size:
        """
        self.bit = [0 for _ in range(size)]
        self.size = size

    def add(self, i, w):
        """
        i番目にwを加える
        :param int i:
        :param int w:
        :return:
        """
        x = i + 1
        while x <= self.size:
            self.bit[x - 1] += w
            x += x & -x
        return

    def sum(self, i):
        """
        [0,i]の合計
        :param int i:
        :return:
        """
        res = 0
        x = i + 1
        while x > 0:
            res += self.bit[x - 1]
            x -= x & -x
        return res

    def search(self, x):
        """
        二分探索。和がx以上となる最小のインデックス(>= 1)を返す
        :param int x:
        :return :
        """
        i = 0
        s = 0
        step = 1 << self.size.bit_length()
        while step:
            if i + step <= self.size and s + self.bit[i + step - 1] < x:
                print(self.bit[i + step - 1], i, step)
                i += step
                s += self.bit[i - 1]
            step >>= 1
        return i

    def __len__(self):
        return self.size
from collections import defaultdict
n=int(input())
a=list(map(int,input().split()))
d=defaultdict(int)
for i in range(n):
  d[a[i]]=i+1
Bit = BinaryIndexedTree(n+1)
ans=0
for i in range(n):
  j=i+1
  i=d[j]
  x=Bit.sum(i)
  ok=i
  ng=-1
  while ok - ng > 1:
    mid=(ok+ng)//2
    if Bit.sum(mid)==x:
      ok=mid
    else:
      ng=mid
  l=ok+1
  ok=i
  ng=n+1
  while ng - ok > 1:
    mid=(ok+ng)//2
    if Bit.sum(mid)==x:
      ok=mid
    else:
      ng=mid
  r=ok
  ans+=j*(i-l+1)*(r-i+1)
  Bit.add(i,1)
print(ans)