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();
		
		if(n%x==0) {
			n--;
		}
		System.out.println(((n/x)+1)*t);
	}
	
}
 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();
		
		if(n%x==0) {
			n--;
		}
		System.out.println(((n/x)+1)*t);
	}
	
} 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();
		
		if(n%x==0) {
			n--;
		}
		System.out.println(((n/x)+1)*t);
	} main {
		Scanner sc = new Scanner(System.in);
	
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();
		
		if(n%x==0) {
			n--;
		}
		System.out.println(((n/x)+1)*t);
	} 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 if(n%x==0) {
			n--;
		} n%x==0 n%x n x 0 {
			n--;
		} n-- n System.out.println(((n/x)+1)*t) System.out.println System.out System System.out ((n/x)+1)*t ((n/x)+1) (n/x) n x 1 t 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();
		
		if(n%x==0) {
			n--;
		}
		System.out.println(((n/x)+1)*t);
	}
	
} 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();
		
		if(n%x==0) {
			n--;
		}
		System.out.println(((n/x)+1)*t);
	}
	
} 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();
		
		if(n%x==0) {
			n--;
		}
		System.out.println(((n/x)+1)*t);
	}
	
}

