Buggy python submission (verdict: Time Limit Exceeded):
import sys
input = sys.stdin.readline

N = int(input())
A = [int(x) for x in input().split()]

A.append(1)

B = [A[0]]
B_cnt = [1]
for i,(x,y) in enumerate(zip(A[:-1],A[1:])):
    if x < y and y < A[i+2]:
        continue
    if x == y:
        B_cnt[-1] += 1
    else:
        B.append(y)
        B_cnt.append(1)

def test(x):
    digit = [0]
    cnt = [0]
    for a,a_cnt in zip(B,B_cnt):
        if digit[-1] < a:
            digit.append(a)
            cnt.append(a_cnt)
            continue
        if digit[-1] == a:
            cnt[-1] += a_cnt
            continue
        while True:
            # 繰り上がり処理をしながら左に戻る
            if digit[-1] <= a:
                break
            n = digit.pop()
            k = cnt.pop()
            if k <= x:
                continue
            if digit[-1] == n-1:
                cnt[-1] += (k-1)//x
            else:
                digit.append(n-1)
                cnt.append((k-1)//x + 1)
        if digit[-1] == a:
            cnt[-1] += a_cnt
        else:
            digit.append(a)
            cnt.append(1+a_cnt)
    return cnt[1] <= x+1

if all(x<y for x,y in zip(A[:-2],A[1:-1])):
    print(1)
    exit()

left = 1 # 無理
right = 2 # 可能?
while not test(right):
    left *= 2
    right *= 2
while right > left + 1:
    mid = (left+right)//2
    if test(mid):
        right = mid
    else:
        left = mid

answer = right
print(answer)

Fixed submission:
import sys
input = sys.stdin.readline

N = int(input())
A = [int(x) for x in input().split()]

A.append(1)

def test(x):
    digit = [0]
    cnt = [0]
    for a in A:
        if digit[-1] < a:
            digit.append(a)
            cnt.append(1)
            continue
        if digit[-1] == a:
            cnt[-1] += 1
            continue
        while True:
            # 繰り上がり処理をしながら左に戻る
            if digit[-1] <= a:
                break
            n = digit.pop()
            k = cnt.pop()
            if k <= x:
                continue
            if digit[-1] == n-1:
                cnt[-1] += (k-1)//x
            else:
                digit.append(n-1)
                cnt.append((k-1)//x + 1)
        if digit[-1] == a:
            cnt[-1] += 1
        else:
            digit.append(a)
            cnt.append(2)
    return cnt[1] <= x+1

if all(x<y for x,y in zip(A[:-2],A[1:-1])):
    print(1)
    exit()

left = 1 # 無理
right = N # 可能
while right > left + 1:
    mid = (left+right)//2
    if test(mid):
        right = mid
    else:
        left = mid

answer = right
print(answer)

Buggy python submission (verdict: Time Limit Exceeded):
import sys
input = sys.stdin.readline

N = int(input())
A = [int(x) for x in input().split()]

A.append(1)

B = [A[0]]
B_cnt = [1]
for i,(x,y) in enumerate(zip(A[:-1],A[1:])):
    if x < y and y < A[i+2]:
        continue
    if x == y:
        B_cnt[-1] += 1
    else:
        B.append(y)
        B_cnt.append(1)

def test(x):
    digit = [0]
    cnt = [0]
    for a,a_cnt in zip(B,B_cnt):
        if digit[-1] < a:
            digit.append(a)
            cnt.append(a_cnt)
            continue
        if digit[-1] == a:
            cnt[-1] += a_cnt
            continue
        while True:
            # 繰り上がり処理をしながら左に戻る
            if digit[-1] <= a:
                break
            n = digit.pop()
            k = cnt.pop()
            if k <= x:
                continue
            if digit[-1] == n-1:
                cnt[-1] += (k-1)//x
            else:
                digit.append(n-1)
                cnt.append((k-1)//x + 1)
        if digit[-1] == a:
            cnt[-1] += a_cnt
        else:
            digit.append(a)
            cnt.append(1+a_cnt)
    return cnt[1] <= x+1

if all(x<y for x,y in zip(A[:-2],A[1:-1])):
    print(1)
    exit()

left = 1 # 無理
right = N # 可能
while right > left + 1:
    mid = (left+right)//2
    if test(mid):
        right = mid
    else:
        left = mid

answer = right
print(answer)

Fixed submission:
import sys
input = sys.stdin.readline

N = int(input())
A = [int(x) for x in input().split()]

A.append(1)

def test(x):
    digit = [0]
    cnt = [0]
    for a in A:
        if digit[-1] < a:
            digit.append(a)
            cnt.append(1)
            continue
        if digit[-1] == a:
            cnt[-1] += 1
            continue
        while True:
            # 繰り上がり処理をしながら左に戻る
            if digit[-1] <= a:
                break
            n = digit.pop()
            k = cnt.pop()
            if k <= x:
                continue
            if digit[-1] == n-1:
                cnt[-1] += (k-1)//x
            else:
                digit.append(n-1)
                cnt.append((k-1)//x + 1)
        if digit[-1] == a:
            cnt[-1] += 1
        else:
            digit.append(a)
            cnt.append(2)
    return cnt[1] <= x+1

if all(x<y for x,y in zip(A[:-2],A[1:-1])):
    print(1)
    exit()

left = 1 # 無理
right = N # 可能
while right > left + 1:
    mid = (left+right)//2
    if test(mid):
        right = mid
    else:
        left = mid

answer = right
print(answer)

Buggy python submission (verdict: Time Limit Exceeded):
import sys
input = sys.stdin.readline

N = int(input())
A = [int(x) for x in input().split()]

A.append(1)

def test(x):
    digit = [0]
    cnt = [0]
    for a in A:
        if digit[-1] < a:
            digit.append(a)
            cnt.append(1)
            continue
        if digit[-1] == a:
            cnt[-1] += 1
            continue
        while True:
            # 繰り上がり処理をしながら左に戻る
            n = digit[-1]
            k = cnt[-1]
            if n <= a:
                break
            digit.pop()
            cnt.pop()
            if k <= x:
                continue
            if digit[-1] == n-1:
                cnt[-1] += (k-1)//x
            else:
                digit.append(n-1)
                cnt.append((k-1)//x + 1)
        if digit[-1] == a:
            cnt[-1] += 1
        else:
            digit.append(a)
            cnt.append(2)
    return cnt[1] <= x+1

if all(x<y for x,y in zip(A[:-2],A[1:-1])):
    print(1)
    exit()

left = 1 # 無理
right = N # 可能
while right > left + 1:
    mid = (left+right)//2
    if test(mid):
        right = mid
    else:
        left = mid

answer = right
print(answer)

Fixed submission:
import sys
input = sys.stdin.readline

N = int(input())
A = [int(x) for x in input().split()]

A.append(1)

def test(x):
    digit = [0]
    cnt = [0]
    for a in A:
        if digit[-1] < a:
            digit.append(a)
            cnt.append(1)
            continue
        if digit[-1] == a:
            cnt[-1] += 1
            continue
        while True:
            # 繰り上がり処理をしながら左に戻る
            if digit[-1] <= a:
                break
            n = digit.pop()
            k = cnt.pop()
            if k <= x:
                continue
            if digit[-1] == n-1:
                cnt[-1] += (k-1)//x
            else:
                digit.append(n-1)
                cnt.append((k-1)//x + 1)
        if digit[-1] == a:
            cnt[-1] += 1
        else:
            digit.append(a)
            cnt.append(2)
    return cnt[1] <= x+1

if all(x<y for x,y in zip(A[:-2],A[1:-1])):
    print(1)
    exit()

left = 1 # 無理
right = N # 可能
while right > left + 1:
    mid = (left+right)//2
    if test(mid):
        right = mid
    else:
        left = mid

answer = right
print(answer)

Buggy python submission (verdict: Time Limit Exceeded):
import sys
input = sys.stdin.readline

N = int(input())
A = [int(x) for x in input().split()]

A.append(1)

def test(x):
    digit = [0]
    cnt = [0]
    for a in A:
        if digit[-1] < a:
            digit.append(a)
            cnt.append(1)
            continue
        if digit[-1] == a:
            cnt[-1] += 1
            continue
        while True:
            # 繰り上がり処理をしながら左に戻る
            n = digit[-1]
            k = cnt[-1]
            if n <= a:
                break
            digit.pop()
            cnt.pop()
            if k <= x:
                continue
            if digit[-1] == n-1:
                cnt[-1] += (k-1)//x
            else:
                digit.append(n-1)
                cnt.append((k-1)//x + 1)
        if digit[-1] == a:
            cnt[-1] += 1
        else:
            digit.append(a)
            cnt.append(2)
    return cnt[1] <= x+1

if all(x<y for x,y in zip(A[:-2],A[1:-1])):
    print(1)
    exit()

left = 1 # 無理
right = 2 # 可能？
while not test(right):
    left = right
    right *= 2
while right > left + 1:
    mid = (left+right)//2
    if test(mid):
        right = mid
    else:
        left = mid

answer = right
print(answer)

Fixed submission:
import sys
input = sys.stdin.readline

N = int(input())
A = [int(x) for x in input().split()]

A.append(1)

def test(x):
    digit = [0]
    cnt = [0]
    for a in A:
        if digit[-1] < a:
            digit.append(a)
            cnt.append(1)
            continue
        if digit[-1] == a:
            cnt[-1] += 1
            continue
        while True:
            # 繰り上がり処理をしながら左に戻る
            if digit[-1] <= a:
                break
            n = digit.pop()
            k = cnt.pop()
            if k <= x:
                continue
            if digit[-1] == n-1:
                cnt[-1] += (k-1)//x
            else:
                digit.append(n-1)
                cnt.append((k-1)//x + 1)
        if digit[-1] == a:
            cnt[-1] += 1
        else:
            digit.append(a)
            cnt.append(2)
    return cnt[1] <= x+1

if all(x<y for x,y in zip(A[:-2],A[1:-1])):
    print(1)
    exit()

left = 1 # 無理
right = N # 可能
while right > left + 1:
    mid = (left+right)//2
    if test(mid):
        right = mid
    else:
        left = mid

answer = right
print(answer)