import java.util.Scanner;

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 cnt = N/X;
			
			if(Math.floorMod(N,X)!=0) {
				cnt++;
			}
			
			
			System.out.println(T*cnt);
	}	
} import java.util.Scanner; Scanner 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 cnt = N/X;
			
			if(Math.floorMod(N,X)!=0) {
				cnt++;
			}
			
			
			System.out.println(T*cnt);
	}	
} 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 cnt = N/X;
			
			if(Math.floorMod(N,X)!=0) {
				cnt++;
			}
			
			
			System.out.println(T*cnt);
	} main {
		Scanner sc = new Scanner(System.in);
			
			int N = sc.nextInt();
			int X = sc.nextInt();
			int T = sc.nextInt();
			int cnt = N/X;
			
			if(Math.floorMod(N,X)!=0) {
				cnt++;
			}
			
			
			System.out.println(T*cnt);
	} 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 cnt = N/X; cnt N/X N X if(Math.floorMod(N,X)!=0) {
				cnt++;
			} Math.floorMod(N,X)!=0 Math.floorMod(N,X) Math.floorMod Math N X 0 {
				cnt++;
			} cnt++ cnt System.out.println(T*cnt) System.out.println System.out System System.out T*cnt T cnt 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 cnt = N/X;
			
			if(Math.floorMod(N,X)!=0) {
				cnt++;
			}
			
			
			System.out.println(T*cnt);
	}	
} 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 cnt = N/X;
			
			if(Math.floorMod(N,X)!=0) {
				cnt++;
			}
			
			
			System.out.println(T*cnt);
	}	
} Main
import java.util.Scanner;

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 cnt = N/X;
			
			if(Math.floorMod(N,X)!=0) {
				cnt++;
			}
			
			
			System.out.println(T*cnt);
	}	
}