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 $(2, 1)$.

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