Problem:
Score : 400 points

Problem Statement

Given are integers A, B, and N.

Find the maximum possible value of floor(Ax/B) - A × floor(x/B) for a non-negative integer x not greater than N.

Here floor(t) denotes the greatest integer not greater than the real number t.

Constraints

1 ≤ A ≤ 10^{6}

1 ≤ B ≤ 10^{12}

1 ≤ N ≤ 10^{12}

All values in input are integers.

Input

Input is given from Standard Input in the following format:

A B N

Output

Print the maximum possible value of floor(Ax/B) - A × floor(x/B) for a non-negative integer x not greater than N, as an integer.

Sample Input 1

5 7 4

Sample Output 1

2

When x=3, floor(Ax/B)-A×floor(x/B) = floor(15/7) - 5×floor(3/7) = 2. This is the maximum value possible.

Sample Input 2

11 10 9

Sample Output 2

9

Solution in Rust (1.42.0) (judge verdict: Wrong Answer)

macro_rules! l {
    () => {{
        let mut buf = String::new();
        std::io::stdin().read_line(&mut buf).unwrap();
        buf.trim()
            .split_whitespace()
            .map(|x| x.parse().unwrap())
            .collect::<Vec<f64>>()
    }};
}

fn main() {
    let (a, b, n) = match &l!()[..] {
        &[a, b, n] => (a, b, n),
        _ => panic!(),
    };

    println!("{}", ((n % b) * (a / b)) as u64);
}