import Foundation

let N = readLine()!.split(separator:" ").map{Int($0)!}
var max = 0
for i in (1...N[2]).reverce(){
  let M = (N[0] * i) / N[1] - N[0] * (i / N[1])
  if(M >= max){
    max = M
  }
}
print(max)
