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(void){
  long long int a,b,n,i,max=0,c,d;
  double fb,fi,fa;
  scanf("%lld%lld%lld",&a,&b,&n);
  /*for(i=0;i<=n;i++){
    fb=(double)b;
    fa=(double)a;
    fi=(double)i;
    c=(long long int)(fa*fi/fb);
    d=i/b;
    if(max<c-a*d){
      max=c-a*d;
    }
  }*/
  i=b-1;
  if(i>n){
    i=n;
  }
  fb=(double)b;
  fa=(double)a;
  fi=(double)i;
  c=(long long int)(fa*fi/fb);
  d=i/b;
  if(max<c-a*d){
    max=c-a*d;
  }
  printf("%lld\n",max);
  return 0;
}