Buggy python submission (verdict: Time Limit Exceeded):
# -*- coding: utf-8 -*-

import sys

def input(): return sys.stdin.readline().strip()
def list2d(a, b, c): return [[c] * b for i in range(a)]
def list3d(a, b, c, d): return [[[d] * c for j in range(b)] for i in range(a)]
def list4d(a, b, c, d, e): return [[[[e] * d for j in range(c)] for j in range(b)] for i in range(a)]
def ceil(x, y=1): return int(-(-x // y))
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(N=None): return list(MAP()) if N is None else [INT() for i in range(N)]
def Yes(): print('Yes')
def No(): print('No')
def YES(): print('YES')
def NO(): print('NO')
sys.setrecursionlimit(10 ** 9)
INF = 10 ** 18
MOD = 10 ** 9 + 7

def rec(cur):
    if len(cur) == 1:
        return cur[0]
    nxt = []
    for i in range(len(cur)-1):
        nxt.append(abs(cur[i] - cur[i+1]))
    return rec(nxt)

N = INT()
A = [a-1 for a in list(map(int, input()))]

ans = rec(A)
print(ans)


Fixed submission:
# -*- coding: utf-8 -*-

import sys

def input(): return sys.stdin.readline().strip()
def list2d(a, b, c): return [[c] * b for i in range(a)]
def list3d(a, b, c, d): return [[[d] * c for j in range(b)] for i in range(a)]
def list4d(a, b, c, d, e): return [[[[e] * d for j in range(c)] for j in range(b)] for i in range(a)]
def ceil(x, y=1): return int(-(-x // y))
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(N=None): return list(MAP()) if N is None else [INT() for i in range(N)]
def Yes(): print('Yes')
def No(): print('No')
def YES(): print('YES')
def NO(): print('NO')
sys.setrecursionlimit(10 ** 9)
INF = 10 ** 18
MOD = 10 ** 9 + 7

def lucas(n, k):
    return (n&k) == k

N = INT()
A = [a-1 for a in list(map(int, input()))]

def check(A):
    mod2 = 0
    for i, a in enumerate(A):
        if a == 1:
            mod2 += lucas(N-1, i)
            mod2 %= 2
    return mod2

res = check(A)
if res == 1:
    print(1)
    exit()

if A.count(1):
    print(0)
    exit()

A = [a//2 for a in A]
res = check(A)
if res == 1:
    print(2)
else:
    print(0)

Buggy python submission (verdict: Runtime Error):
# -*- coding: utf-8 -*-

import sys

def input(): return sys.stdin.readline().strip()
def list2d(a, b, c): return [[c] * b for i in range(a)]
def list3d(a, b, c, d): return [[[d] * c for j in range(b)] for i in range(a)]
def list4d(a, b, c, d, e): return [[[[e] * d for j in range(c)] for j in range(b)] for i in range(a)]
def ceil(x, y=1): return int(-(-x // y))
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(N=None): return list(MAP()) if N is None else [INT() for i in range(N)]
def Yes(): print('Yes')
def No(): print('No')
def YES(): print('YES')
def NO(): print('NO')
sys.setrecursionlimit(10 ** 9)
INF = 10 ** 18
MOD = 10 ** 9 + 7

N = INT()
A = list(map(int, input()))

while max(A) >= 2:
    tmp = []
    for i in range(len(A)-1):
        tmp.append(abs(A[i] - A[i+1]))
    A = tmp

while len(A) > 2:
    tmp1 = [A[0]]
    for i in range(1, len(A)):
        if A[i] != tmp1[-1]:
            tmp1.append(A[i])
    tmp2 = []
    for i in range(len(tmp1)-1):
        tmp2.append(abs(tmp1[i] - tmp1[i+1]))
    A = tmp2
if len(A) == 1:
    print(A[0])
else:
    print(abs(A[0] - A[1]))


Fixed submission:
# -*- coding: utf-8 -*-

import sys

def input(): return sys.stdin.readline().strip()
def list2d(a, b, c): return [[c] * b for i in range(a)]
def list3d(a, b, c, d): return [[[d] * c for j in range(b)] for i in range(a)]
def list4d(a, b, c, d, e): return [[[[e] * d for j in range(c)] for j in range(b)] for i in range(a)]
def ceil(x, y=1): return int(-(-x // y))
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(N=None): return list(MAP()) if N is None else [INT() for i in range(N)]
def Yes(): print('Yes')
def No(): print('No')
def YES(): print('YES')
def NO(): print('NO')
sys.setrecursionlimit(10 ** 9)
INF = 10 ** 18
MOD = 10 ** 9 + 7

def lucas(n, k):
    return (n&k) == k

N = INT()
A = [a-1 for a in list(map(int, input()))]

def check(A):
    mod2 = 0
    for i, a in enumerate(A):
        if a == 1:
            mod2 += lucas(N-1, i)
            mod2 %= 2
    return mod2

res = check(A)
if res == 1:
    print(1)
    exit()

if A.count(1):
    print(0)
    exit()

A = [a//2 for a in A]
res = check(A)
if res == 1:
    print(2)
else:
    print(0)

Buggy python submission (verdict: Runtime Error):
# -*- coding: utf-8 -*-

import sys

def input(): return sys.stdin.readline().strip()
def list2d(a, b, c): return [[c] * b for i in range(a)]
def list3d(a, b, c, d): return [[[d] * c for j in range(b)] for i in range(a)]
def list4d(a, b, c, d, e): return [[[[e] * d for j in range(c)] for j in range(b)] for i in range(a)]
def ceil(x, y=1): return int(-(-x // y))
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(N=None): return list(MAP()) if N is None else [INT() for i in range(N)]
def Yes(): print('Yes')
def No(): print('No')
def YES(): print('YES')
def NO(): print('NO')
sys.setrecursionlimit(10 ** 9)
INF = 10 ** 18
MOD = 10 ** 9 + 7

N = INT()
A = list(map(int, input()))

while max(A) >= 2:
    tmp = []
    for i in range(len(A)-1):
        tmp.append(abs(A[i] - A[i+1]))
    A = tmp

while len(A) > 2:
    tmp1 = [A[0]]
    for i in range(1, len(A)):
        if A[i] != tmp1[-1]:
            tmp1.append(A[i])
    tmp2 = []
    for i in range(len(tmp1)-1):
        tmp2.append(abs(tmp1[i] - tmp1[i+1]))
    A = tmp2
print(abs(A[0] - A[1]))


Fixed submission:
# -*- coding: utf-8 -*-

import sys

def input(): return sys.stdin.readline().strip()
def list2d(a, b, c): return [[c] * b for i in range(a)]
def list3d(a, b, c, d): return [[[d] * c for j in range(b)] for i in range(a)]
def list4d(a, b, c, d, e): return [[[[e] * d for j in range(c)] for j in range(b)] for i in range(a)]
def ceil(x, y=1): return int(-(-x // y))
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(N=None): return list(MAP()) if N is None else [INT() for i in range(N)]
def Yes(): print('Yes')
def No(): print('No')
def YES(): print('YES')
def NO(): print('NO')
sys.setrecursionlimit(10 ** 9)
INF = 10 ** 18
MOD = 10 ** 9 + 7

def lucas(n, k):
    return (n&k) == k

N = INT()
A = [a-1 for a in list(map(int, input()))]

def check(A):
    mod2 = 0
    for i, a in enumerate(A):
        if a == 1:
            mod2 += lucas(N-1, i)
            mod2 %= 2
    return mod2

res = check(A)
if res == 1:
    print(1)
    exit()

if A.count(1):
    print(0)
    exit()

A = [a//2 for a in A]
res = check(A)
if res == 1:
    print(2)
else:
    print(0)