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: Accepted)

#!/usr/bin/env python
import sys
from collections import Counter
from itertools import permutations, combinations
#from fractions import gcd
from math import gcd
from math import ceil, floor
import bisect
sys.setrecursionlimit(10 ** 6)
inf = float("inf")

def input():
    return sys.stdin.readline()[:-1]


def main():
    a, b, n = map(int, input().split())
    x = min(b-1, n)
    print(floor(a*x/b) - a*floor(x/b))

if __name__ == '__main__':
    main()