import java.util.*;

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

class Main
{
    public static void main(String[] args) {
        
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();
        
        int result = n / x;
        int judge = n % x;
        if (judge != 0) {
            result++;
        } 
        int answer = result * t;
        
        System.out.println(answer);
    }
}