To and Fro.txt

The Guardians of the Galaxy have just landed on Earth.

There are N cities in a row numbered from 1 to N.

The cost of going from a city with number i to a city with number j is the remainder when (i+j) is divided by (n+1).

The Guardians want to visit every city but in the minimum cost. What is the minimum cost that will be incurred?
Problem Constraints
1 <= N <= 10000000



Input Format
A single integer N denoting the number of cities.



Output Format
Minimum cost to be able to travel to each city



Example Input
 3


Example Output
 1


Example Explanation
 Tour would be 1 -> 3 -> 2.

...............Algorithm...........................

1 n 2 n-1 3 n-2 if you observe some pattern then you will find that this will give our optimal answer.because as try to make i+j to n+1 as much as possible
.


int Solution::solve(int A) {
    // that will take 0(n^2).
    return (A-1)/2;
    
}