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 PyPy3 (7.3.0) (judge verdict: Accepted)

import sys
input = sys.stdin.readline
import bisect
import math


# 持っているビスケットを叩き、1枚増やす
# ビスケット A枚を 1円に交換する
# 1円をビスケット B枚に交換する
def main():
    a, b, n = input_list()
    x = min(b-1, n)
    aa = math.floor((a*x)/b) - (a * math.floor(x/b))
    print(aa)

def bi(num, a, b, x):
    print((a * num) + (b * len(str(b))))
    if (a * num) + (b * len(str(b))) <= x:
        return False
    return True

def input_list():
    return list(map(int, input().split()))


def input_list_str():
    return list(map(str, input().split()))


if __name__ == "__main__":
    main()