import Foundation

func readInts() -> [Int] {
    return readLine()!.split(separator: " ").map { Int($0)! }
}

func main() {
    let a = readInts()
    let N = a[0]
    let X = a[1]
    let T = a[2]
    let d = Int(ceil(Double(N) / Double(X)))
    print("\(T * d)")
}

main()
