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 i=n%x;
		int j=n/x;
		if(i==0) {
			System.out.println(t*j);
		}
		else {
			System.out.println(t*j+t);
		}
		sc.close();
				
	}
} 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 i=n%x;
		int j=n/x;
		if(i==0) {
			System.out.println(t*j);
		}
		else {
			System.out.println(t*j+t);
		}
		sc.close();
				
	}
} 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 i=n%x;
		int j=n/x;
		if(i==0) {
			System.out.println(t*j);
		}
		else {
			System.out.println(t*j+t);
		}
		sc.close();
				
	} main {
		Scanner sc=new Scanner(System.in);
		int n=sc.nextInt();
		int x=sc.nextInt();
		int t=sc.nextInt();
		
		int i=n%x;
		int j=n/x;
		if(i==0) {
			System.out.println(t*j);
		}
		else {
			System.out.println(t*j+t);
		}
		sc.close();
				
	} 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 i=n%x; i n%x n x int j=n/x; j n/x n x if(i==0) {
			System.out.println(t*j);
		}
		else {
			System.out.println(t*j+t);
		} i==0 i 0 {
			System.out.println(t*j);
		} System.out.println(t*j) System.out.println System.out System System.out t*j t j {
			System.out.println(t*j+t);
		} System.out.println(t*j+t) System.out.println System.out System System.out t*j+t t*j t j t sc.close() sc.close sc 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 i=n%x;
		int j=n/x;
		if(i==0) {
			System.out.println(t*j);
		}
		else {
			System.out.println(t*j+t);
		}
		sc.close();
				
	}
} 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 i=n%x;
		int j=n/x;
		if(i==0) {
			System.out.println(t*j);
		}
		else {
			System.out.println(t*j+t);
		}
		sc.close();
				
	}
} 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 i=n%x;
		int j=n/x;
		if(i==0) {
			System.out.println(t*j);
		}
		else {
			System.out.println(t*j+t);
		}
		sc.close();
				
	}
}