import Foundation
let arr=readLine()!.split{$0==" "}.map{Int(String($0))!}
var a=arr[0]
var b=arr[1]
var c=arr[2]
var max = 0
for i in 0..<c+1 {
  let j = floor(Float(a*i)/Float(b))-floor(Float(i)/Float(b))
    if Int(j) > max {
        max = Int(j)
    }
}
print(max)