import java.io.PrintWriter;
import java.util.Scanner;

public class Main {
    void solve(Scanner sc, PrintWriter pw) {
        int N = sc.nextInt();
        int X = sc.nextInt();
        int T = sc.nextInt();
        pw.println((N + X - 1) / X * T);
    }
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        PrintWriter pw = new PrintWriter(System.out);
        new Main().solve(sc, pw);
        pw.flush();
        pw.close();
        sc.close();
    }
} import java.io.PrintWriter; PrintWriter java.io import java.util.Scanner; Scanner java.util public class Main {
    void solve(Scanner sc, PrintWriter pw) {
        int N = sc.nextInt();
        int X = sc.nextInt();
        int T = sc.nextInt();
        pw.println((N + X - 1) / X * T);
    }
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        PrintWriter pw = new PrintWriter(System.out);
        new Main().solve(sc, pw);
        pw.flush();
        pw.close();
        sc.close();
    }
} Main void solve(Scanner sc, PrintWriter pw) {
        int N = sc.nextInt();
        int X = sc.nextInt();
        int T = sc.nextInt();
        pw.println((N + X - 1) / X * T);
    } solve {
        int N = sc.nextInt();
        int X = sc.nextInt();
        int T = sc.nextInt();
        pw.println((N + X - 1) / X * T);
    } int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc int X = sc.nextInt(); X sc.nextInt() sc.nextInt sc int T = sc.nextInt(); T sc.nextInt() sc.nextInt sc pw.println((N + X - 1) / X * T) pw.println pw (N + X - 1) / X * T (N + X - 1) / X (N + X - 1) N + X N X 1 X T Scanner sc sc PrintWriter pw pw public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        PrintWriter pw = new PrintWriter(System.out);
        new Main().solve(sc, pw);
        pw.flush();
        pw.close();
        sc.close();
    } main {
        Scanner sc = new Scanner(System.in);
        PrintWriter pw = new PrintWriter(System.out);
        new Main().solve(sc, pw);
        pw.flush();
        pw.close();
        sc.close();
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) PrintWriter pw = new PrintWriter(System.out); pw new PrintWriter(System.out) new Main().solve(sc, pw) new Main().solve new Main() sc pw pw.flush() pw.flush pw pw.close() pw.close pw sc.close() sc.close sc String[] args args public class Main {
    void solve(Scanner sc, PrintWriter pw) {
        int N = sc.nextInt();
        int X = sc.nextInt();
        int T = sc.nextInt();
        pw.println((N + X - 1) / X * T);
    }
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        PrintWriter pw = new PrintWriter(System.out);
        new Main().solve(sc, pw);
        pw.flush();
        pw.close();
        sc.close();
    }
} public class Main {
    void solve(Scanner sc, PrintWriter pw) {
        int N = sc.nextInt();
        int X = sc.nextInt();
        int T = sc.nextInt();
        pw.println((N + X - 1) / X * T);
    }
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        PrintWriter pw = new PrintWriter(System.out);
        new Main().solve(sc, pw);
        pw.flush();
        pw.close();
        sc.close();
    }
} Main
import java.io.PrintWriter;
import java.util.Scanner;

public class Main {
    void solve(Scanner sc, PrintWriter pw) {
        int N = sc.nextInt();
        int X = sc.nextInt();
        int T = sc.nextInt();
        pw.println((N + X - 1) / X * T);
    }
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        PrintWriter pw = new PrintWriter(System.out);
        new Main().solve(sc, pw);
        pw.flush();
        pw.close();
        sc.close();
    }
}
