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: Time Limit Exceeded)

import sys
import os
import math

def file_input():
    f = open('../Beginner_Contest_165/input.txt', 'r')
    sys.stdin = f

def main():
    #file_input()
    # input()
    A,B,N=map(int, input().split())

    max=0
    for x in range(N+1):
        # ans=int(A*x/B)-A*int(x/B)
        min,_=math.modf(x/B)
        ans=int(A*min)
        if ans > max:
            max=ans

    print(max)

if __name__ == '__main__':
    main()