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 C# (Mono-csc 3.5.0) (judge verdict: Accepted)

using System;
using System.Linq;

namespace program{
    public class AtCoder{
        public static void Main(string[] args){
            // 整数の入力
            var input = Console.ReadLine().Split(' ');
    		long A = long.Parse(input[0]);
    		long B = long.Parse(input[1]);
    		long N = long.Parse(input[2]);
    		var answerX = B - 1;
    		if(answerX > N) answerX = N;
    		var answer = (long)(A * answerX / B) - A * (long)(answerX / B);
    		Console.WriteLine(answer);
        }
    }
}