import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        java.util.Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();
        int c = 0;
        c = (n%x == 0)?n/x:n/x+1;
        System.out.println(c*t);
    }
} import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args) {
        java.util.Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();
        int c = 0;
        c = (n%x == 0)?n/x:n/x+1;
        System.out.println(c*t);
    }
} Main public static void main(String[] args) {
        java.util.Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();
        int c = 0;
        c = (n%x == 0)?n/x:n/x+1;
        System.out.println(c*t);
    } main {
        java.util.Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();
        int c = 0;
        c = (n%x == 0)?n/x:n/x+1;
        System.out.println(c*t);
    } java.util.Scanner sc = new Scanner(System.in); sc new Scanner(System.in) 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 int c = 0; c 0 c = (n%x == 0)?n/x:n/x+1 c (n%x == 0)?n/x:n/x+1 (n%x == 0) n%x n x 0 n/x n x n/x+1 n/x n x 1 System.out.println(c*t) System.out.println System.out System System.out c*t c t String[] args args public class Main {
    public static void main(String[] args) {
        java.util.Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();
        int c = 0;
        c = (n%x == 0)?n/x:n/x+1;
        System.out.println(c*t);
    }
} public class Main {
    public static void main(String[] args) {
        java.util.Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();
        int c = 0;
        c = (n%x == 0)?n/x:n/x+1;
        System.out.println(c*t);
    }
} Main
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        java.util.Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();
        int c = 0;
        c = (n%x == 0)?n/x:n/x+1;
        System.out.println(c*t);
    }
}