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: Time Limit Exceeded)

#include<stdio.h>

int main(void){
    int a;
	unsigned long int b,n;
	unsigned long int x;
	unsigned long int flr1,flr2;
	unsigned long int tmp=0;
	unsigned long int ans;
	
    scanf("%d %lu %lu",&a,&b,&n  );
		for(x=1;x<=n;x++){
			flr1=a*x / b;
			flr2= x / b;
			ans = flr1 - a*flr2;
			if(tmp <= ans){
				tmp= ans ;
			}
		}
		printf("%lu",tmp);
	}