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 count = n / x;
		int answer = 0;
		
		if(n % x == 0) answer = count;
		else answer = count + 1;
			
		System.out.println(answer * t);
			
		
	
		
		
		
	}

} 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 count = n / x;
		int answer = 0;
		
		if(n % x == 0) answer = count;
		else answer = count + 1;
			
		System.out.println(answer * t);
			
		
	
		
		
		
	}

} 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 count = n / x;
		int answer = 0;
		
		if(n % x == 0) answer = count;
		else answer = count + 1;
			
		System.out.println(answer * t);
			
		
	
		
		
		
	} 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 count = n / x;
		int answer = 0;
		
		if(n % x == 0) answer = count;
		else answer = count + 1;
			
		System.out.println(answer * 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 int count = n / x; count n / x n x int answer = 0; answer 0 if(n % x == 0) answer = count;
		else answer = count + 1; n % x == 0 n % x n x 0 answer = count answer count answer = count + 1 answer count + 1 count 1 System.out.println(answer * t) System.out.println System.out System System.out answer * t answer t 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 count = n / x;
		int answer = 0;
		
		if(n % x == 0) answer = count;
		else answer = count + 1;
			
		System.out.println(answer * t);
			
		
	
		
		
		
	}

} 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 count = n / x;
		int answer = 0;
		
		if(n % x == 0) answer = count;
		else answer = count + 1;
			
		System.out.println(answer * t);
			
		
	
		
		
		
	}

} 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 count = n / x;
		int answer = 0;
		
		if(n % x == 0) answer = count;
		else answer = count + 1;
			
		System.out.println(answer * t);
			
		
	
		
		
		
	}

}
