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>
#include<stdlib.h>
#include<string.h>
#include <assert.h>
 
int main(void){
	long long int a,b,c;
    long long int ans;
	scanf("%lld",&a);
    scanf("%lld",&b);
    scanf("%lld",&c);
    long long int x = 0;
 
    if(c<b){
      x = c;
    }
    else{
      x = b-1;
    }
 
 
 
 
    ans = (a*x/b) - a*(x/b);
 
 
    printf("%lld\n",ans);
 
 
		return 0;
}