[Solution] Integers that sum to the same value CodeChef Solution

Problem

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 $i + j = N$.

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Explanation:

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 $1$.

Explanation:

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

Explanation:

The two pairs are $(1, 2)$ and $(2, 1)$.