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 (Clang 10.0.0) (judge verdict: Time Limit Exceeded)

#include<stdio.h>

int main() {
	long int a, b, n, m,ma,mb,ans;
	scanf("%ld %ld %ld", &a, &b, &n);
	ma = (a*0) / b;
	mb = a*(0 / b);
	ans = ma - mb;
	for (long int i = 1; i <= n; i++) {
		ma = (a*i) / b;
		mb = a*(i / b);
		m = ma - mb;
		if (m > ans) {
			ans = m;
		}
	}
	printf("%ld", ans);
}