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()
{
	int a;
	long long b;
	long long n;
	scanf("%d",&a);
	scanf("%lld",&b);
	scanf("%lld",&n);
	int maxpoint=0;
  	long long x=1;
	while(1)
	{
		int temp=(int)(a*x/b)-a*(int)(x/b);
		if(maxpoint<temp)maxpoint=temp;
      	//printf("x:%d,%d-%d=%d\n",x,(int)(a*x/b),a*(int)(x/b),temp);
      	x+=1;
      	if(x>b)break;
	}
	printf("%d",maxpoint);
}