func readInt(separator: Character) -> [Int] {
  return readLine()!.split(separator: separator).map { Int($0)! }
}
let abn = readInt(separator: " ")
let a = abn[0], b = abn[1], n = abn[2]
var maxValue = 0
var x = n
while x > 0 {
  let m = a*x / b - a * (x / b)
  let tmp = maxValue
  maxValue = max(m, maxValue)
  if tmp > maxValue { break }
  x -= 1
}
print(maxValue)