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: Time Limit Exceeded)

using System;
using static System.Console;
using System.Linq;

namespace AC
{
   public class shiokara
   {
      static void Main(string[] args)
      {
         long[] basedata = ReadLine().Split(' ').Select(long.Parse).ToArray();
         long ans = 0;
         long tmp;
         for(long i = 1; i <= basedata[2]; i++){
             tmp = calc(basedata[0], basedata[1], i);
             if(tmp > ans) ans = tmp;
         }
         WriteLine(ans);
      }

      public static long calc(long a, long b, long x)
      {
          double one = a * x / b;
          if(x < b) return (long)Math.Floor(one);
          double two = x / b;
          return (long)Math.Floor(one) - a * (long)Math.Floor(two);
      }
   }
}