import java.util.*;
public 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 res;

        if(N%X==0){
            res = N*T/X;
        }else{
            res = T*(N/X+1);
        }
        
        System.out.println(res);
                
            
        
        
        
        
        
        }
    } import java.util.*; util.* java public 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 res;

        if(N%X==0){
            res = N*T/X;
        }else{
            res = T*(N/X+1);
        }
        
        System.out.println(res);
                
            
        
        
        
        
        
        }
    } 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 res;

        if(N%X==0){
            res = N*T/X;
        }else{
            res = T*(N/X+1);
        }
        
        System.out.println(res);
                
            
        
        
        
        
        
        } main {
		Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int X = sc.nextInt();
        int T = sc.nextInt();
        
        int res;

        if(N%X==0){
            res = N*T/X;
        }else{
            res = T*(N/X+1);
        }
        
        System.out.println(res);
                
            
        
        
        
        
        
        } 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 res; res if(N%X==0){
            res = N*T/X;
        }else{
            res = T*(N/X+1);
        } N%X==0 N%X N X 0 {
            res = N*T/X;
        } res = N*T/X res N*T/X N*T N T X {
            res = T*(N/X+1);
        } res = T*(N/X+1) res T*(N/X+1) T (N/X+1) N/X N X 1 System.out.println(res) System.out.println System.out System System.out res String[] args args public 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 res;

        if(N%X==0){
            res = N*T/X;
        }else{
            res = T*(N/X+1);
        }
        
        System.out.println(res);
                
            
        
        
        
        
        
        }
    } public 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 res;

        if(N%X==0){
            res = N*T/X;
        }else{
            res = T*(N/X+1);
        }
        
        System.out.println(res);
                
            
        
        
        
        
        
        }
    } Main
import java.util.*;
public 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 res;

        if(N%X==0){
            res = N*T/X;
        }else{
            res = T*(N/X+1);
        }
        
        System.out.println(res);
                
            
        
        
        
        
        
        }
    }