import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		
		Scanner sc = new Scanner (System.in);
		
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();
		int min =0;

		if(n%x==0) {
			min = (n/x)*t;
		}else if(n%x != 0) {
			min = (n/x+1)*t;
		}
		
		System.out.println(min);

	}

} import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		
		Scanner sc = new Scanner (System.in);
		
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();
		int min =0;

		if(n%x==0) {
			min = (n/x)*t;
		}else if(n%x != 0) {
			min = (n/x+1)*t;
		}
		
		System.out.println(min);

	}

} Main public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		
		Scanner sc = new Scanner (System.in);
		
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();
		int min =0;

		if(n%x==0) {
			min = (n/x)*t;
		}else if(n%x != 0) {
			min = (n/x+1)*t;
		}
		
		System.out.println(min);

	} main {
		// TODO 自動生成されたメソッド・スタブ
		
		Scanner sc = new Scanner (System.in);
		
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();
		int min =0;

		if(n%x==0) {
			min = (n/x)*t;
		}else if(n%x != 0) {
			min = (n/x+1)*t;
		}
		
		System.out.println(min);

	} 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 min =0; min 0 if(n%x==0) {
			min = (n/x)*t;
		}else if(n%x != 0) {
			min = (n/x+1)*t;
		} n%x==0 n%x n x 0 {
			min = (n/x)*t;
		} min = (n/x)*t min (n/x)*t (n/x) n x t if(n%x != 0) {
			min = (n/x+1)*t;
		} n%x != 0 n%x n x 0 {
			min = (n/x+1)*t;
		} min = (n/x+1)*t min (n/x+1)*t (n/x+1) n/x n x 1 t System.out.println(min) System.out.println System.out System System.out min String[] args args public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		
		Scanner sc = new Scanner (System.in);
		
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();
		int min =0;

		if(n%x==0) {
			min = (n/x)*t;
		}else if(n%x != 0) {
			min = (n/x+1)*t;
		}
		
		System.out.println(min);

	}

} public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		
		Scanner sc = new Scanner (System.in);
		
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();
		int min =0;

		if(n%x==0) {
			min = (n/x)*t;
		}else if(n%x != 0) {
			min = (n/x+1)*t;
		}
		
		System.out.println(min);

	}

} Main
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		
		Scanner sc = new Scanner (System.in);
		
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();
		int min =0;

		if(n%x==0) {
			min = (n/x)*t;
		}else if(n%x != 0) {
			min = (n/x+1)*t;
		}
		
		System.out.println(min);

	}

}