A. ^{-1}
import sys
def solve():
input = sys.stdin.readline
mod = 10 ** 9 + 7
n, x = list(map(int, input().rstrip('\n').split()))
p = list(map(int, input().rstrip('\n').split()))
print(p.index(x) + 1)
if __name__ == '__main__':
solve()
B. Playing Cards Validation
import sys
import collections
def solve():
input = sys.stdin.readline
mod = 10 ** 9 + 7
n = int(input().rstrip('\n'))
d = collections.defaultdict(int)
for i in range(n):
s = str(input().rstrip('\n'))
if not s[0] in ["H", "D", "C", "S"]:
print("No")
exit()
if not s[1] in ["A", "2", "3", "4", "5", "6", "7", "8", "9", "T", "J", "Q", "K"]:
print("No")
exit()
if s in d:
print("No")
exit()
d[s]
print("Yes")
if __name__ == '__main__':
solve()
C. Ladder Takahashi
import sys
import collections
def solve():
input = sys.stdin.readline
mod = 10 ** 9 + 7
n = int(input().rstrip('\n'))
tmd = collections.defaultdict(list)
for i in range(n):
tma, tmb = list(map(int, input().rstrip('\n').split()))
tmd[tma-1] += [tmb-1]
tmd[tmb-1] += [tma-1]
ql = [[0, 0]]
ql = collections.deque(ql)
fq = collections.defaultdict(list)
fq[0]
while True:
if len(ql) != 0:
cost, tmp = ql.popleft()
for tmv in tmd[tmp]:
if tmv not in fq:
ql.append([cost + 1, tmv])
fq[tmv]
else:
break
print(max(fq.keys()) + 1)
if __name__ == '__main__':
solve()