import Foundation
 
let input_line: String = readLine()!
let split: [String] = input_line.components(separatedBy: " ")
 
let X = Int(split[0])!
let T = Int(split[1])!
let N = Int(split[2])!

if (N % X == 0){
    print(N / X * T)
}else{
    print(N / X * T + T)
}