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)

import math
listA=[] #appendのために宣言が必要
while True:
    try:
        listA.append(list(map(int,input().split())))

    except:
        break;
        #または、quit(),os.exit()をして止める。

a = listA[0][0]
b = listA[0][1]
n = listA[0][2]

old = 0
for x in range(1,n):
  if x == 1:
    old = math.floor(a*x/b)-a*math.floor(x/b)
  else:
    current = math.floor(a*x/b)-a*math.floor(x/b)
    if old < current:
      old = current
    
print (old)