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 (GCC 9.2.1) (judge verdict: Wrong Answer)

#include<stdio.h>
#include<math.h>
int main()
{
  int a,b,n;
  scanf("%d %d %d",&a,&b,&n);
  int i,t,max=0;
  for(i=1;i<=n;i++)
  {
    if(b>n)
    {
    t=floor((a*i)/b)-(a*floor(i/b));
    if(max<t)
      max=t;
    }
    else
    {
      t=floor((a*(b-1))/b)-(a*floor((b-1)/b));
      if(max<t)
      max=t;
    }
  }
  printf("%d",max);
}