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: Accepted)

#include<stdio.h>
int main()
{
long long int a,b,n,i,max,c,d,e,f,h;
  
  scanf("%lld %lld %lld",&a,&b,&n);

  
  c=a*n/b;
   e=n/b; 
   f=a*e;
  max=c-f;
  
  if(a==b || b>n) 
  {printf("%lld",max);}
  
  
 else{
     
      d=b-1;
     c=(a*d)/b;
     e=d/b;
     f=a*e;
     if(max<(c-f)) max=c-f;
     
      
    printf("%lld",max);}

  
return 0;
}