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 JavaScript (Node.js 12.16.1) (judge verdict: Accepted)

const Main = (input) => {
  const tmp = input.trim().split(' ').map(n => parseInt(n))
  const A = tmp[0]
  const B = tmp[1]
  const N = tmp[2]

  let x = Math.min(B - 1, N)

  const result = Math.floor(A * x / B) - (A * Math.floor(x / B))

  console.log(result)
  return result
}

Main(require('fs').readFileSync('/dev/stdin', 'utf8'))