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 (Clang 10.0.0) (judge verdict: Time Limit Exceeded)

#include<stdio.h>  
int main() 
{
  long int a,b,n,i,j;
  scanf("%ld %ld %ld",&a,&b,&n);
  long int max,tmp,com;
  max=(a*0/b)-a*(0/b);
  for(i=-100; i<=n; i++){
    com=(a*i/b)-a*(i/b);
    for(j=1; j<=n; j++){
      if(max<com)
	max=com;
    }
  }
  printf("%ld\n",max);
  return 0;
}