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 Python (3.8.2) (judge verdict: Wrong Answer)

def val(a, b, x):
	return int((a * x) / b) - a * int(x / b)

def naive(a, b, n):
	ans = 0
	for i in range(1, n + 1):
		ans = max(ans, int((a * i) / b) - a * int(i / b))
	return ans

def main(a, b, n):
	if n % b == 0:
		return val(a, b, n - 1)
	else:
		return max(val(a, b, n), val(a, b, (n // b) * b - 1))

# n = 10000
# for a in range(1, 10):
# 	for b in range(1, 100):
# 		if naive(a, b, n) != main(a, b, n):
# 			print(a, b, naive(a, b, n), main(a, b, n))

a, b, n = list(map(int, input().split()))
print(main(a, b, n))