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# (.NET Core 3.1.201) (judge verdict: Wrong Answer)

using System;
using System.Linq;

namespace ConsoleApp1 {
    public class Class1 {
        static void Main(string[] args) {
            var num = Console.ReadLine().Trim().Split(' ').Select(_ => long.Parse(_)).ToArray();
            var A = num[0];
            var B = num[1];
            var N = num[2];
            long tmp;
            long ans = 0;

            if(N < B) {
                tmp = N;
            } else {
                tmp = B - 1;
            }
            ans = Test(tmp, A, B);

            Console.Write(ans);
        }

        static long Test(long x, float A, float B) {
            var n = Math.Floor(A * x / B) - A * Math.Floor(x / B);
            return (long)n;
        }
    }
}