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: Runtime Error)

#include<stdio.h>
#include<math.h>
int main(void)
{
    double a,b,n;
    scanf("%lf %lf %lf",&a,&b,&n);
    int i=1;
    int m;
    int max[510000];
    for(i=1;i<=n;i++){
        max[i]=floor(a*i/b)-a*floor(i/b);
    }
    m=max[1];
    for(i=1;i<=n;i++){
        if(max[i]>m){
            m=max[i];
        }
    }
    printf("%d\n",m);
    return 0;
}