Problem:
 Score : 100 points    Problem Statement How many ways are there to choose two distinct positive integers totaling N , disregarding the order?      Constraints  1 \leq N \leq 10^6  N is an integer.         Input Input is given from Standard Input in the following format:  N       Output Print the answer.        Sample Input 1 4      Sample Output 1 1  There is only one way to choose two distinct integers totaling 4 : to choose 1 and 3 . (Choosing 3 and 1 is not considered different from this.)       Sample Input 2 999999      Sample Output 2 499999

Solution (Python):
n=int(input())
cnt=0
if n %2==0:
  print(n//2 -1)
else:print(n//2)

Solution (Python):
n = int(input())
if n%2 == 0:
  print(int(n/2-1))
else:
  print(int((n-1)/2))

Solution (Python):
N = int(input())
print((N + 1) // 2 - 1)

Solution (Python):
n = int(input())
ans = 0
for i in range(1,n//2+1):
  if i != n-i:
    ans += 1
print(ans)

Solution (Python):
n = int(input())
print((n-1)//2)

Solution (Python):
n = int(input())
print((n-1)//2)

Solution (Python):
N = int(input())
print((N-1)//2)

Solution (Python):
import math
a = int(input())
b = math.ceil(a/2)
print(b-1)

Solution (Python):
N = int(input())
print((N - 1) // 2)

Solution (Python):
import math






s=int(input())

a = math.ceil(s/2)
print(a-1)

Solution (Python):
n = int(input())
if n % 2 != 0:
    print(n//2)
else:
    print(n//2-1)

Solution (Python):
n = int(input())

ans = 0
for i in range(1, n):
  tmp = n - i
  if i < tmp:
    ans  += 1
    
print(ans)

Solution (Python):
n = int(input())

if n % 2 == 0:
    print(n//2-1)
else:
    print(n//2)

Solution (Python):
n = int(input())
if n % 2 == 0:
    print(n // 2 - 1)
else:
    print(n // 2)

Solution (Python):

import sys
def input():
    return sys.stdin.readline()[:-1]

def main():
    N = int(input())

    ans = N // 2
    if N % 2 == 0:
        ans -= 1
    print(ans)

if __name__ == '__main__':
    main()

Solution (Python):
N=int(input())

if N % 2:
  print(N//2)
  exit()
  
print((N-1)//2)

Solution (Python):

n=int(input())
if n%2==0:
    n-=1
print(n//2)

Solution (Python):
def main():
    import sys
    input = sys.stdin.readline
    sys.setrecursionlimit(10**7)
    from collections import Counter, deque
    from collections import defaultdict
    from itertools import combinations, permutations, accumulate, groupby, product
    from bisect import bisect_left,bisect_right
    from heapq import heapify, heappop, heappush
    from math import floor, ceil,pi,factorial
    from operator import itemgetter
    def I(): return int(input())
    def MI(): return map(int, input().split())
    def LI(): return list(map(int, input().split()))
    def LI2(): return [int(input()) for i in range(n)]
    def MXI(): return [[LI()]for i in range(n)]
    def SI(): return input().rstrip()
    def printns(x): print('\n'.join(x))
    def printni(x): print('\n'.join(list(map(str,x))))
    inf = 10**17
    mod = 10**9 + 7

    
    '''w,h=MI()
    lis=[LI() for i in range(h)]
    step=[[0,-1],[-1,0],[-1,1],[0,-1],[1,0],[0,1]]
    print(lis)
    for i in range(h):
        for j in range(w):
            if lis[i][j]==0:
                count=0
                for x,y in step:
                    if 0<=i+x<h and 0<=j+y<w and lis[i+x][j+y]==1:
                        count+=1
            if count==6:
                lis[i][j]=1
    ans=0
    for i in range(h):
        for j in range(w):
            if lis[i][j]==1:
                for x,y in step:
                    if not (0<=i+x<h and 0<=j+y<w):
                        ans+=1
                    elif lis[i+x][j+y]==0:
                        ans+=1
            print(ans)
    print(ans)
                        
    print(lis)'''
    n=I()
    if n%2==0:
        print(n//2-1)
    else:
        print((n-1)//2)
if __name__=="__main__":
    main()

Solution (Python):
n = int(input())
if n & 1:
  print((n - 1) // 2)
else:
  print(n // 2 - 1)

Solution (Python):
n = int(input())
print((n - 1) // 2)

Solution (Python):
def main():
    n = int(input())

    if n == 1 or n == 2:
        ans = 0
    else:
        if n % 2 == 0:
            ans = n // 2 - 1
        else:
            ans = n // 2

    print(ans)


if __name__ == "__main__":
    main()

Solution (Python):
N = int(input())
print((N-1)//2)

Solution (Python):
print((int(input())-1)//2)

Solution (Python):
N = int (input ())
if N%2 == 0:
  print (round(N/2-1))
else:
  print (N//2)

Solution (Python):
n = int(input())
if n % 2 == 0:
    print(n // 2 - 1)
else:
    print(n//2)

Solution (Python):
n = int(input())
if n%2 == 0:
    ans = n//2-1
else:
    ans = n//2
print(ans)

Solution (Python):
n = int(input())
if n%2 == 0:
    print(n//2-1)
else:
    print(n//2)

Solution (Python):
n = int(input())
print(n // 2 if n % 2 == 1 else (n - 1) // 2 )

Solution (Python):
import math
n = int(input())
print(math.ceil(n / 2) - 1)

Solution (Python):
'''
Created on 2020/08/20

@author: harurun
'''
def main():
  import sys
  pin=sys.stdin.readline
  pout=sys.stdout.write
  perr=sys.stderr.write
  
  N=int(pin())
  print((N-1)//2)
  return 

main()

Solution (Python):
print((int(input())-1)//2)

Solution (Python):
n=int(input())
print((n-1)//2)

Solution (Python):

n=int(input())
ans=0
for i in range(1,(n+1)//2):
    ans+=1
print(ans)

Solution (Python):
print((int(input())-1)//2)

Solution (Python):
n=int(input())
if n%2==0:
    print((n-2)//2)
else:
    print(((n-1)//2))

Solution (Python):
a = int(input())
if a % 2 == 0:
  print(int(a / 2 - 1))
else:
  print(int(a // 2))

Solution (Python):
n = int(input())
ans = n//2
if n%2 == 0:
    ans -= 1
print(ans)

Solution (Python):
print((int(input())-1)//2)

Solution (Python):

N = int(input())
print(N // 2 - int(N % 2 == 0))

Solution (Python):
p, q = divmod(int(input()), 2)
print(p - (q ^ 1))

Solution (Python):
N=int(input())
print((N-1)//2)

Solution (Python):
N=int(input())

if N%2==0:
  print(N//2-1)
else:
  print(N//2)

Solution (Python):
print((int(input()) - 1)//2)

Solution (Python):
n = int(input())
print(max((n - 1)// 2, 0))

Solution (Python):
n=int(input())
if n%2==0:
  ans = n//2 -1
else:
  ans = n//2
print(ans)

Solution (Python):
n = int(input())
if n % 2 == 0:
    n -= 1
print(n // 2)

Solution (Python):
n= int(input())

if n%2==0:
  print(n//2-1)
else:
  print(n//2)

Solution (Python):
n = int(input())
ans = (n - 1) // 2
print(ans)

Solution (Python):
n = int(input())
ans = 0
for i in range(1, n):
    if i >= n - i:
        break
    ans += 1
print(ans)

Solution (Python):
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians
from itertools import accumulate, permutations, combinations, product, groupby
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from bisect import bisect, bisect_left
from fractions import gcd
from heapq import heappush, heappop
from functools import reduce
def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
def ZIP(n): return zip(*(MAP() for _ in range(n)))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 998244353

N = INT()
print((N-1)//2)

Solution (Python):
n = int(input())
if n % 2 == 0:
    print((n - 2) // 2)
else:
    print(n // 2)

Solution (Python):
import sys

input = sys.stdin.readline


def main():
    N = int(input())

    if N % 2 == 0:
        ans = (N - 2) // 2
    else:
        ans = (N - 1) // 2

    print(ans)


if __name__ == "__main__":
    main()

Solution (Python):
print((int(input())-1)//2)

Solution (Python):
n = int(input())

print((n-1)//2)

Solution (Python):
print((int(input()) - 1) // 2)

Solution (Python):
N = int(input())
if(N%2==0):
  print(int((N/2)-1))
else:
  print(int(N/2))

Solution (Python):
n = int(input())
print((n+1)//2 -1)

Solution (Python):
def main():
    N = int(input())

    ans = 0
    for i in range(1, N):
        j = N - i

        if i != j:
            ans += 1

    print(ans//2)
    
if __name__ == "__main__":
    main()

Solution (Python):
N = int(input())
ans = 0
for i in range(1,N//2+1):
  if i != N-i:
    ans += 1
print(ans)

Solution (Python):
N = int(input())
print((N-1)//2)

Solution (Python):
import sys
input = sys.stdin.buffer.readline




def RD(): return sys.stdin.read()
def II(): return int(input())
def MI(): return map(int,input().split())
def MF(): return map(float,input().split())
def LI(): return list(map(int,input().split()))
def LF(): return list(map(float,input().split()))
def TI(): return tuple(map(int,input().split()))


def main():
	n=II()

	print((n-1)//2)









if __name__ == "__main__":
	main()

Solution (Python):
n = int(input())
if n%2 == 0:
    print(n//2-1)
else:
    print(n//2)

Solution (Python):


N=  int(input())

if N%2 == 0:
    print(N//2-1)
else:
    print(N//2)

Solution (Python):



from fractions import gcd
from itertools import combinations,permutations,accumulate 

from collections import deque,defaultdict,Counter
import decimal
import re












import sys
sys.setrecursionlimit(10000000)
mod = 10**9 + 7

def readInts():
  return list(map(int,input().split()))
def I():
  return int(input())
n = I()
if n%2 == 0:
    print(n//2 - 1)
else:
    print((n+1)//2 - 1)

Solution (Python):
N = int(input())
if N%2==0:
    print(N//2-1)
else:
    print(N//2)

Solution (Python):
n = int(input())
ans = 0
print(n//2 if n%2!=0 else n//2-1)

Solution (Python):
n = int(input())
if n%2 == 0:
    print((n-1)//2)
else:
    print(n//2)

Solution (Python):
N = int(input())
print((N-1)//2)

Solution (Python):
n=int(input())
print(-(-n//2)-1)

Solution (Python):
print((int(input())-1)//2)

Solution (Python):
n = int(input())
print((n-1)//2)

Solution (Python):
print((int(input())-1)//2)

Solution (Python):
n = int(input())
if n % 2 == 0:
    print(round(n / 2 - 1))
else:
    print((n // 2))

Solution (Python):





n = int(input())

print(n//2 if n&1 else n//2-1)

Solution (Python):
n=int(input())
print((n+1)//2-1)

Solution (Python):
n=int(input())
print((n-1)//2)

Solution (Python):
n=int(input())
x=n//2
if n%2==1:
  print(x)
else:
  print(x-1)

Solution (Python):
n=int(input())
print((n-1)//2)

Solution (Python):
N = int(input())
if N % 2:
    print(N // 2)
else:
    print(N // 2 - 1)

Solution (Python):
n=int(input())
s=set()
for i in range(1,n):
  j=n-i
  if i==j:continue
  t=[i,j]
  t.sort()
  key=str(t[0])+str([1])
  s.add(key)
print(len(s))

Solution (Python):
n = int(input())

print(n//2) if n % 2 else print(n//2-1)

Solution (Python):
n=int(input())

ans = (n-1)//2

print(ans)

Solution (Python):
print((int(input()) - 1)//2)

Solution (Python):
import math 
N= int(input())
ans = math.ceil(N/2)-1
print(ans)

Solution (Python):
def resolve():
    S = int(input())
    if S%2 == 0:
        print(S//2-1)
    else:
        print((S-1)//2)
resolve()

Solution (Python):
n = int(input())
cnt = 0
for i in range(1, n//2+1):
    if i != n - i and n - i > 0:
        cnt += 1
print(cnt)

Solution (Python):
n = int(input())
if n%2==0:
    print(n//2-1)
else:
    print(n//2)

Solution (Python):
n = int(input())
if n % 2 == 1:
    print(n//2)
else:
    print(n//2-1)

Solution (Python):
N = int(input())
if N % 2 == 0:
  ans = N//2-1
else:
  ans = N//2
print(ans)

Solution (Python):
N=int(input())
N-=1
print(N//2)

Solution (Python):
n=int(input())
print(n//2 if n%2==1 else n//2-1)

Solution (Python):
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, tan, asin, acos, atan, radians, degrees
from itertools import accumulate, permutations, combinations, combinations_with_replacement, product, groupby
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from bisect import bisect, bisect_left, insort, insort_left
from fractions import gcd
from heapq import heappush, heappop
from functools import reduce
def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
def ZIP(n): return zip(*(MAP() for _ in range(n)))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10**9 + 7


N = INT()

print(-(-N//2)-1)

Solution (Python):
print((int(input())-1)//2)

Solution (Python):
a=int(input())
print((a-1)//2)

Solution (Python):
n = int(input())
ans = 0 - -n//2 - 1
print(ans)

Solution (Python):
N = int(input())

if N % 2 == 0:
    print(N // 2 - 1)
else:
    print(N // 2)

Solution (Python):
N = int(input())
N -= (1-N%2)
print(N//2)

Solution (Python):
N = int(input())
ans = N // 2
if N % 2 == 0: ans -= 1
print(ans)

Solution (Python):
print((int(input()) - 1) // 2)

Solution (Python):
import math;print(int(math.floor(int(input())-.5)/2))

Solution (Python):
N = int(input())
print((N-1)//2)

Solution (Python):
n=int(input())
if n%2==0:
	print(n//2 -1)
else:
	print(n//2)

Solution (Python):
n = int(input())
if n == 1:
    print(0)
elif n == 2:
    print(0)
else:
    print( (n-1) // 2)

Solution (Python):
print((int(input())-1)//2)

Solution (Python):
n=int(input())
print((n-1)//2)

Solution (Python):
n = int(input())

if n % 2 == 0:
  print(n // 2 - 1)
else:
  print((n-1) // 2)

Solution (Python):
from statistics import median


from fractions import gcd
from itertools import combinations 
from collections import deque
from collections import defaultdict
import bisect










import sys
sys.setrecursionlimit(10000000)
mod = 10**9 + 7

def readInts():
  return list(map(int,input().split()))
def I():
  return int(input())
n = I()
print((n+1)//2 - 1)

Solution (Python):
import sys
sys.setrecursionlimit(10**8)
def ii(): return int(sys.stdin.readline())
def mi(): return map(int, sys.stdin.readline().split())
def li(): return list(map(int, sys.stdin.readline().split()))
def li2(N): return [list(map(int, sys.stdin.readline().split())) for i in range(N)]
def dp2(ini, i, j): return [[ini]*i for i2 in range(j)]
def dp3(ini, i, j, k): return [[[ini]*i for i2 in range(j)] for i3 in range(k)]





N = ii()

print((N-1)//2)

Solution (Python):
import sys
sys.setrecursionlimit(10**8)
def ii(): return int(sys.stdin.readline())
def mi(): return map(int, sys.stdin.readline().split())
def li(): return list(map(int, sys.stdin.readline().split()))
def li2(N): return [list(map(int, sys.stdin.readline().split())) for i in range(N)]
def dp2(ini, i, j): return [[ini]*i for i2 in range(j)]
def dp3(ini, i, j, k): return [[[ini]*i for i2 in range(j)] for i3 in range(k)]





N = ii()

if N % 2:
    print(N//2)
else:
    print((N-1)//2)

Solution (Python):
a = (int)(input())
print((a-1)//2)

Solution (Python):
n = int(input())
if n%2==0:
    print(n//2-1)
else:
    print(n//2)

Solution (Python):
a = int(input())
if a%2 == 1:
    print(int(a/2))
else:
    print(int(a/2) - 1)

Solution (Python):
import sys
input = sys.stdin.readline

def I(): return int(input())
def MI(): return map(int, input().split())
def LI(): return list(map(int, input().split()))

def main():
    mod=10**9+7
    N=I()
    ans=0
    for i in range(1,N):
        j=N-i
        if i!=j:
            ans+=1
    print(ans//2)
        
        

main()

Solution (Python):
n = int(input())
print((n-1)//2)

Solution (Python):
n = int(input())
if n%2 == 0:
  print(n//2-1)
else:
  print((n-1)//2)

Solution (Python):
print((int(input())-1)//2)

Solution (Python):
print((int(input())-1)//2)

Solution (Python):
n=int(input())
if n%2==0:
    ans=n//2 -1
else:
    ans=n//2
print(ans)

Solution (Python):
v=int(input())
print(int(v/2-1*(v%2==0)))

Solution (Python):
N=int(input())
print(N//2-1 if N%1 else (N-1)//2)

Solution (Python):
N = int(input())

if N % 2 == 0:
  ans = N // 2 - 1
else:
  ans = N // 2

print(ans)

Solution (Python):
n = int(input())
if n%2==0:
  print(int(n//2)-1)
else:
  print(int(n//2))

Solution (Python):
n = int(input())
print(n // 2 if n % 2 == 1 else n // 2 -1)

Solution (Python):
N = int(input())
if N == 1:
  print(0)
else:
  print((N+1)//2-1)

Solution (Python):
print((int(input())-1)//2)

Solution (Python):
print((int(input())-1)//2)

Solution (Python):
N=int(input())
if(N%2==1):
  print(N//2)
else:
  print(N//2-1)

Solution (Python):
n = int(input())
print(-(-n//2)-1)

Solution (Python):
N=int(input())
print((N-1)//2)

Solution (Python):
n=int(input())
print((n-1)//2)

Solution (Python):
n = int(input())
if n % 2 == 0:
  print(n // 2 - 1)
else:
  print(n // 2)

Solution (Python):
N = int(input())
ans = []
for i in range(1, N//2+1):
  if i != (N-i):
    ans.append((i, N-i))
print(len(set(ans)))

Solution (Python):
N = int(input())
print((N+1)//2-1)

Solution (Python):
n = int(input())

print(n - n//2 -1)

Solution (Python):
n = int(input())
if n % 2 == 1:
  n += 1
print(n//2-1)

Solution (Python):
n=int(input())
print((n-1)//2)

Solution (Python):
n = int(input())

c = n//2
if(n%2 == 0):c-=1
print(c)

Solution (Python):
n = int(input())

print((n-1)//2)

Solution (Python):
num = int(input())






half = int(num / 2)

count = 0

for i in range(1, half + 1):
    a = i
    b = num - i

    if a != b:
        count += 1
    
print(count)

Solution (Python):
A = int(input())
if A % 2 == 0:
    print(A//2-1)
else:
    print(A//2)

Solution (Python):
n = int(input())
print((n - 1) // 2)

Solution (Python):
n = int(input())

if n % 2 == 0:
    print((n-1)//2)
else:
    print(n//2)

Solution (Python):
import math

N = int(input())
print(math.ceil(N/2) - 1)

Solution (Python):
def resolve():
    n=int(input())
    print((n-1)//2)
resolve()

Solution (Python):
def resolve():
    n=int(input())
    if n%2==0:
        print(n//2-1)
    else:
        print(n//2)
resolve()

Solution (Python):
import sys
sys.setrecursionlimit(10 ** 5 + 10)
def input(): return sys.stdin.readline().strip()

def resolve():

    N=int(input())
    print((N-1)//2)

resolve()

Solution (Python):
import sys

sys.setrecursionlimit(10 ** 7)
f_inf = float('inf')
mod = 10 ** 9 + 7


def resolve():
    n = int(input())

    res = 0
    for i in range(1, (n + 1) // 2):
        if i != n - i:
            res += 1

    print(res)


if __name__ == '__main__':
    resolve()

Solution (Python):
print(0--int(input())//2-1)

Solution (Python):
def main():
    import sys
    input = sys.stdin.readline
    sys.setrecursionlimit(10**7)
    from collections import Counter, deque
    
    from itertools import combinations, permutations, accumulate, groupby, product
    from bisect import bisect_left,bisect_right
    from heapq import heapify, heappop, heappush
    from math import floor, ceil
    

    
    

    n = int(input())
    if n%2 == 0:
        print(n//2-1)
    else:
        print(n//2)

if __name__ == '__main__':
    main()

Solution (Python):
n=int(input())
ans=0
for i in range(1,n+1):
    if i<n-i:
        ans+=1
print(ans)

Solution (Python):
N=int(input())
if N%2==0:
    N-=1
N//=2
print(N)

Solution (Python):
n = int(input())
if n%2==0:
    print(n//2-1)
else:
    print(n//2)

Solution (Python):
N=int(input())
if N%2==1:
    print(int(float(N-1)/2))
else:
    print(int(float(N-2)/2))

Solution (Python):
n = int(input())
if n % 2 == 0:
    print(n // 2 - 1)
else:
    print(n // 2)

Solution (Python):
a=int(input())
if a%2==0:
    ans=(a/2)-1
else:
    ans=a//2
print(int(ans))

Solution (Python):
import sys
import math
a = int(input())
if (a % 2 == 0):
    print(a // 2 - 1)
else:
    print((a+1)//2-1)

Solution (Python):
import sys


def input():
    return sys.stdin.readline().strip()


sys.setrecursionlimit(10 ** 9)
MOD = 998244353


def main():
    N = int(input())
    if N % 2 == 0:
        print(N // 2 - 1)
    else:
        print(N // 2)


if __name__ == "__main__":
    main()

Solution (Python):
N = int(input())
print((N - 1) // 2)

Solution (Python):
n = int(input())
print((n-1)//2)

Solution (Python):
N = int(input())

if N % 2 == 0:
    print(N//2-1)
else:
    print(N//2)

Solution (Python):

N=int(input())
if N%2==0: print(N//2-1)
else: print(N//2)

Solution (Python):
import sys
def input(): return sys.stdin.readline().rstrip()
def main():
    n=int(input())
    print((n-1)//2)

if __name__=='__main__':
    main()

Solution (Python):
import sys
def input(): return sys.stdin.readline().rstrip()
def main():
    n=int(input())
    print((n-1)//2)

if __name__=='__main__':
    main()

Solution (Python):
print((int(input())+1)//2-1)

Solution (Python):
n = int(input())

if n % 2 == 0:
  print(n // 2 - 1)
else:
  print((n - 1) // 2)

Solution (Python):
print((int(input())-1) // 2)

Solution (Python):
print((int(input())-1) // 2)

Solution (Python):

N = int(input())

if N % 2 == 1:
	N += 1
	
print(int(N / 2 - 1))

Solution (Python):
N = int(input())
cnt=0
for i in range(1, N):
    k = N-i
    if i<k:
        cnt+=1
print(cnt)

Solution (Python):
print(int((int(input())-1)/2))

Solution (Python):
N=int(input())
print( (N-1)//2)

Solution (Python):
n = int(input())
a,b = divmod(n,2)
if b == 0:
  a -= 1
print(a)

Solution (Python):
N=int(input())

M=[]

for i in range (1,N):
    if N-i!=i:
        M.append(N-i)

print(len(M)//2)

Solution (Python):
print(-(-int(input())//2)-1)

Solution (Python):

n = int(input())
print((n - 1) // 2)

Solution (Python):
N = int(input())
print((N - 1) // 2)

Solution (Python):
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
sys.setrecursionlimit(10 ** 7)

from math import floor

n = int(readline())
print(floor((n - 1) / 2))

Solution (Python):
n=int(input())
if n%2==0:
  print(n//2-1)
else:
  print((n+1)//2-1)

Solution (Python):
n = int(input())
iteration = n
ex = 0
count = 0
for i in range(1,n):
    ex = iteration-i
    
    if ex <=i:
        break
    else:
        count += 1
print(count)

Solution (Python):


N = int(input().split()[0])
ans = (N - 1) // 2
print(ans)

Solution (Python):
import math
print(int(math.ceil(int(input())/2)-1))

Solution (Python):
N=int(input())
if N%2==0:
    print(N//2-1)
else:
    print(N//2)

Solution (Python):
N = int(input())
print((N-1)//2)

Solution (Python):
N = int(input())-1
print(N//2)

Solution (Python):
import sys
import copy
import math
import bisect
import pprint
import bisect
from functools import reduce
from copy import deepcopy
from collections import deque

def lcm(x, y):
    return (x * y) // math.gcd(x, y)

if __name__ == '__main__':
    a = int(input())

    print((a-1)//2)

Solution (Python):
N = int(input())
print((N - 1) // 2)

Solution (Python):
n = int(input())

print((n-1)//2)

Solution (Python):
print((int(input())-1)//2)

Solution (Python):
N = int(input())

print((N-1)//2)

Solution (Python):
import math
n=int(input())
print(math.ceil(n/2-1))

Solution (Python):
n = int(input())

if n % 2 == 0:
    print(n//2 - 1)
else:
    print((n-1)//2)

Solution (Python):
n = int(input())

print((n - (n+1)%2)//2)

Solution (Python):
N = int(input())
print((N-1)//2)

Solution (Python):
n = int(input())

if n % 2 == 0:
    print(int(n / 2) - 1)
else:
    print(int((n - 1) / 2))

Solution (Python):
N=int(input());
print((N-1)//2);

Solution (Python):
n = int(input())
if n%2 == 0:
    print(n//2-1)
else:
    print(n//2)

Solution (Python):
N=int(input())
print(N//2-1 if N%2==0 else N//2)

Solution (Python):
n = int(input())
if n % 2 == 0:
    print(n // 2 - 1)
else:
    print(n // 2)

Solution (Python):
n = int(input())
print((n - 1)//2)

Solution (Python):
n = int(input())

if n % 2 == 0:
	print(n//2-1)
else:
	print(n//2)

Solution (Python):
import math
n = int(input())
print(math.ceil(n/2)-1)

Solution (Python):
n = int(input())

x = 0
if n%2 == 0:
    x = 1
print(n // 2 - x)

Solution (Python):
print((int(input())-1)//2)

Solution (Python):
def main():
    number = int(input())
    print(number // 2 - (number + 1) % 2)


if __name__ == '__main__':
    main()

Solution (Python):
n=int(input())
print((n-1)//2 if n%2==1 else n//2-1)

Solution (Python):
print((int(input())-1)//2)

Solution (Python):
x=int(input())
print((x-1)//2)

Solution (Python):









import sys



ipti = sys.stdin.readline
MOD = 10 ** 9 + 7
INF = float('INF')
sys.setrecursionlimit(10 ** 5)

def main():
    n = int(input())
    if n % 2 == 0:
        print(n//2 - 1)
    else:
        print(n//2)

if __name__ == '__main__':
    main()

Solution (Python):
N = int(input())

print(N//2 - (1 - N%2))

Solution (Python):
n = int(input())
if n>=3:
    if n%2==0:
        print(n//2-1)
    else:
        print(n//2)
else:
    print(0)

Solution (Python):
N=int(input())
print((N-1)//2)

Solution (Python):
n=int(input())
print((n-1)//2)

Solution (Python):
N = int(input())
if N % 2 == 0:
  print(N // 2 - 1)
else:
  print(N // 2)

Solution (Python):
N = int(input())
print(N//2 if N%2 else N//2-1)

Solution (Python):
n = int(input())
print((n-1)//2)

Solution (Python):
N = int(input())

if N % 2 == 0:
    ans = N // 2
    ans -= 1
else:
    ans = (N - 1) // 2

print(ans)

Solution (Python):
print((int(input())-1)//2)

Solution (Python):
N = int(input())
print((N-1)//2)

Solution (Python):
n = int(input())
print(n//2-1 if n%2 == 0 else n//2)

Solution (Python):
N = int(input())

print(int((N-1)/2))

Solution (Python):
N = int(input())

if N % 2 == 0:
    print(N // 2 - 1)
else:
    print(N // 2)

Solution (Python):
N = int(input())

if N % 2 == 0:
    N -= 1
print(N // 2)

Solution (Python):
print((int(input()) - 1) // 2)

Solution (Python):


n = int(input())
print(int((n - 1) / 2) if n % 2 == 1 else int(n / 2) - 1)

Solution (Python):
N = int(input())
answer = (N - 1) // 2
print(answer)

Solution (Python):
print((int(input())-1)//2)

Solution (Python):
n=int(input())
if n%2==0: print(n//2-1)
else: print(n//2)

Solution (Python):
N = int(input())




print((N-1)//2)

Solution (Python):
i  = int(input())

if i%2 == 0:
  print(i//2-1)
else:
  print(i//2)

Solution (Python):
N = int(input())
if N % 2 == 1:
    print((N-1)//2)
else:
    print((N//2)-1)

Solution (Python):
N = int(input())
print((N - 1) // 2)

Solution (Python):
N = int(input())
if N % 2 == 1:
    print(int(N / 2))
else :
    print(int(N / 2 - 1))

Solution (Python):
def main():
    N = int(input())
    print((N-1)//2)

if __name__ == '__main__':
    main()

Solution (Python):
n=int(input())
print(int(n/2)-1 if n%2==0 else int((n-1)/2))

Solution (Python):
N = int(input())
if N%2 == 0:
    print(N//2-1)
else:
    print((N-1)//2)

Solution (Python):
from sys import stdin
N = int(stdin.readline().rstrip())
if N % 2 == 0:
    print(N//2-1)
else:
    print((N-1)//2)

Solution (Python):
def examA():
    N = I()
    ans = (N-1)//2
    print(ans)
    return

def examB():
    ans = 0
    print(ans)
    return

def examC():
    ans = 0
    print(ans)
    return

def examD():
    ans = 0
    print(ans)
    return

def examE():
    ans = 0
    print(ans)
    return

def examF():
    ans = 0
    print(ans)
    return

import sys,copy,bisect,itertools,heapq,math
from heapq import heappop,heappush,heapify
from collections import Counter,defaultdict,deque
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))
def LFI(): return list(map(float,sys.stdin.readline().split()))
def LSI(): return list(map(str,sys.stdin.readline().split()))
def LS(): return sys.stdin.readline().split()
def SI(): return sys.stdin.readline().strip()
global mod,mod2,inf,alphabet
mod = 10**9 + 7
mod2 = 998244353
inf = 10**18
alphabet = [chr(ord('a') + i) for i in range(26)]

if __name__ == '__main__':
    examA()

"""

"""

Solution (Python):
print(-(-int(input())//2)-1)

Solution (Python):


n=int(input())

if n<=2:
    print(0)
elif n%2==0:
    print(int(n/2-1))
else:
    print(int(n/2-0.5))

Solution (Python):
N = int(input())
print((N - 1) // 2)

Solution (Python):
from collections import defaultdict

n = int(input())

ans = 0
d = defaultdict(int)
for i in range(1, n+1):
	d[i]+=1
	j = n-i
	if d[j] > 0: continue
	if j == i: continue
	if j > 0: ans+=1

print(ans)

Solution (Python):
N = int(input())
if N % 2 == 0:
    print(N // 2 - 1)
else:
    print(N // 2)

Solution (Python):
a = int(input())

print(a//2-(a%2==0))

Solution (Python):
a = int(input())

print(a//2-(a%2==0))

Solution (Python):
a = int(input())

print(a//2-(a%2==0))

Solution (Python):
n = int(input())

if(n%2==0):
    print(n//2-1)
else:
    print(n//2)

Solution (Python):
n = int(input());print(n//2 if n%2==1 else n//2 -1)

Solution (Python):
def main():
    N = int(input())
    if N%2==0:
        print(N//2-1)
    else:
        print((N-1)//2)
if __name__ == '__main__':
    main()

Solution (Python):
def main():
    N = int(input())
    if N%2==0:
        print(N//2-1)
    else:
        print((N-1)//2)
if __name__ == '__main__':
    main()

Solution (Python):
print((int(input()) - 1) // 2)

Solution (Python):
N=int(input())
print((N-1)//2)

Solution (Python):
def main(n: int):
    if n % 2 == 0:
        print(int((n / 2) - 1))
    else:
        print(int((n - 1) / 2))


if __name__ == "__main__":
    n = int(input())

    main(n)

Solution (Python):
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,copy,functools
import time,random

sys.setrecursionlimit(10**7)
inf = 10**20
eps = 1.0 / 10**10
mod = 10**9+7
dd = [(-1,0),(0,1),(1,0),(0,-1)]
ddn = [(-1,0),(-1,1),(0,1),(1,1),(1,0),(1,-1),(0,-1),(-1,-1)]

def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(): return [list(map(int, l.split())) for l in sys.stdin.readlines()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()
def pf(s): return print(s, flush=True)
def pe(s): return print(str(s), file=sys.stderr)
def JA(a, sep): return sep.join(map(str, a))
def JAA(a, s, t): return s.join(t.join(map(str, b)) for b in a)


def main():
    n = I()
    r = n // 2
    if n % 2 == 0:
        r -= 1

    return r


print(main())

Solution (Python):
print((int(input())-1)//2)

Solution (Python):
from sys import stdin
import sys

def ria(sep = ''):
    if sep == '' :
        return list(map(int, input().split())) 
    else: return list(map(int, input().split(sep)))
def rsa(sep = ''):
    if sep == '' :
        return input().split() 
    else: return input().split(sep)
def ri(): return int(input())
def rd(): return float(input())
def rs(): return input()

def main():
    N = ri()
    if N % 2 == 0:
        print(N // 2 - 1)
    else:
        print(N // 2)


if __name__ == "__main__":
    main()

Solution (Python):
N = int(input())
print(int(N / 2)) if N % 2 != 0 else print(int(N / 2) - 1)

Solution (Python):
def f(N):
    if N%2==0:
        return N//2-1
    else:
        return N//2
N=int(input())
print(f(N))

Solution (Python):
import sys


def solve():
    readline = sys.stdin.buffer.readline
    mod = 10 ** 9 + 7
    n = int(readline())
    cnt = 0
    for i in range(1, n):
        if i + 1 <= n - i <= n:
            cnt += 1
    print(cnt)


if __name__ == '__main__':
    solve()

Solution (Python):
N = int(input())
print((N+1) // 2 - 1)

Solution (Python):
n = int(input())

if n % 2 == 0:
	print(int(n/2) - 1)
elif n % 2 == 1:
	print(n // 2)

Solution (Python):
n = int(input())
print(n//2-1 if n%2==0 else (n-1)//2)

Solution (Python):
n = int(input())
if n % 2 == 0:
    print(n//2-1)
else:
    print(n//2)

Solution (Python):
N = int(input())
if N % 2 == 0:
  ans = (N / 2) - 1
else:
  ans = (N - 1) / 2
print(int(ans))

Solution (Python):
n = int(input())

if n%2==0:
	print(int(n/2-1))
else:
	print(n//2)

Solution (Python):



n = int(input())
s = 0

if n % 2 == 0 :
 s = n / 2 - 1
else :
 s = n // 2

print(int(s))

Solution (Python):
n = int(input())
if n % 2 == 1:
  print((n-1)//2)
else:
  print((n-2)//2)

Solution (Python):
print((int(input())-1)//2)