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>
 
int main()
{
    unsigned long long int a,b,n;
    scanf("%llu %llu %llu",&a, &b,&n);
    unsigned long long int max=0;
    unsigned long long int ans=0;
    if(b<=n)
    {
    for(int i = b-1;i<=n;i+=b){
    ans=((i*a)/b)-a*(i/b);
    if(ans>max){
    max=ans;
    }
    }
    }
    else{
    ans=((n*a)/b)-a*(n/b);
    if(ans>max){
        max=ans;
                }
        }
        
     printf("%llu",max);
    return 0;
}