import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		// 整数の入力
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();

		int makeNum = 0;
		int num = 0;

		while(makeNum < n){
			makeNum = makeNum + x;
			num = num + t;
		}

		System.out.println(num);

		sc.close();
	}
} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		// 整数の入力
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();

		int makeNum = 0;
		int num = 0;

		while(makeNum < n){
			makeNum = makeNum + x;
			num = num + t;
		}

		System.out.println(num);

		sc.close();
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		// 整数の入力
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();

		int makeNum = 0;
		int num = 0;

		while(makeNum < n){
			makeNum = makeNum + x;
			num = num + t;
		}

		System.out.println(num);

		sc.close();
	} main {
		Scanner sc = new Scanner(System.in);

		// 整数の入力
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();

		int makeNum = 0;
		int num = 0;

		while(makeNum < n){
			makeNum = makeNum + x;
			num = num + t;
		}

		System.out.println(num);

		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 makeNum = 0; makeNum 0 int num = 0; num 0 while(makeNum < n){
			makeNum = makeNum + x;
			num = num + t;
		} makeNum < n makeNum n {
			makeNum = makeNum + x;
			num = num + t;
		} makeNum = makeNum + x makeNum makeNum + x makeNum x num = num + t num num + t num t System.out.println(num) System.out.println System.out System System.out num sc.close() sc.close sc String[] args args public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		// 整数の入力
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();

		int makeNum = 0;
		int num = 0;

		while(makeNum < n){
			makeNum = makeNum + x;
			num = num + t;
		}

		System.out.println(num);

		sc.close();
	}
} public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		// 整数の入力
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();

		int makeNum = 0;
		int num = 0;

		while(makeNum < n){
			makeNum = makeNum + x;
			num = num + t;
		}

		System.out.println(num);

		sc.close();
	}
} Main
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		// 整数の入力
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();

		int makeNum = 0;
		int num = 0;

		while(makeNum < n){
			makeNum = makeNum + x;
			num = num + t;
		}

		System.out.println(num);

		sc.close();
	}
}