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>

void main(void){
    long a,b,n,x,res,res1,res2, max=0;

    scanf("%ld %ld %ld", &a,&b,&n);

    for(x=0;x<=n;x++){
        if(b>x)
            res1= 0;
        else 
            res1 = a*x/b;
        
        if((a*x) < b )
            res2 = 0; 
        else
            res2 = x/b;
        
        res = res1 -a*res2;
        if(res>=max){
            max=res;
        }else
            break;
    }
    printf("%ld\n", max);
}