Alice has a positive integer N. She is wondering how many ordered pairs of positive integers (i, j) exist such that i + j = N. 

Help Alice figure out the answer.

Note that since the pairs are ordered, (1, 2) and (2, 1) are considered different.

------ Input Format ------ 

The first and only line of input contains a single integer N.

------ Output Format ------ 

Print a single integer, the number of ordered pairs of positive integers (i, j) such that i + j = N.

------ Constraints ------ 

$1 ≤ N ≤ 100$

----- Sample Input 1 ------ 
1
----- Sample Output 1 ------ 
0
----- explanation 1 ------ 
As both integers must be positive, the minimum sum must be $1 + 1 = 2$. Therefore there are no pairs of positive integers adding up to $1$.

----- Sample Input 2 ------ 
2
----- Sample Output 2 ------ 
1
----- explanation 2 ------ 
$(1,1)$ is the only pair whose sum is $2$. Every other pair has a sum of at least $3$.

----- Sample Input 3 ------ 
3
----- Sample Output 3 ------ 
2
----- explanation 3 ------ 
The two pairs are $(1, 2)$ and $(2, 1)$.

Difficulty: EASY

Solutions:
a = int(input())
if a % 2 == 0:
	print(a - 1)
else:
	print(a - 1)


n = int(input())
c = 0
for i in range(n):
	for j in range(n):
		if i + j == n:
			c += 1
print(c)


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


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


x = int(input())
print(x - 1)


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


N = int(input())
ans = 0
for i in range(1, N + 1):
	for j in range(1, N + 1):
		if i + j == N:
			ans += 1
print(ans)


a = int(input())
print(a - 1)


t = int(input())
print(t - 1)


n = int(input())
L = []
for i in range(1, n):
	for j in range(1, n):
		if i + j == n:
			L.append((i, j))
print(len(L))


print(int(input()) - 1)


T = int(input())
print(T - 1)


N = int(input())
count = 0
if N >= 2:
	for i in range(1, N):
		for j in range(1, N):
			if i + j == N:
				count += 1
			else:
				pass
print(count)


N = int(input())
for num in range(0, N):
	N += num
print(num)


n = int(input())
count = 0
for i in range(n):
	for j in range(n):
		a = i + j
		if a == n:
			count += 1
print(count)


n = int(input())
for i in range(n):
	a = i + (n - i)
print(i)


import math
n = int(input())
print(n - 1)