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 Java (OpenJDK 11.0.6) (judge verdict: Wrong Answer)

import java.io.InputStream;
import java.io.PrintStream;
import java.util.Scanner;

public class Main {

  public static void main(String[] args) {
    resolve(System.in, System.out);
  }

  static void resolve(InputStream is, PrintStream pw) {
    Scanner sc = new Scanner(is);
    long a = Long.parseLong(sc.next());
    long b = Long.parseLong(sc.next());
    long n = Long.parseLong(sc.next());
    long maxX = n;
    if (b == 1) {
      pw.println(0);
      return;
    }
    double ad = (double) a;
    double bd = (double) b;
    while (calc(ad, bd, maxX) == 0 && maxX > 0) {
      maxX--;
    }
    pw.println(
      calc(ad, bd, maxX)
    );
  }

  static long calc(double ad, double bd, long x) {
    return (long) Math.floor(ad * x / bd) - (long) ad * (long) Math.floor(x / bd);
  }
}