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 total = 0;
		int res = 0;
		
		while(total < n) {
			
			res += t;
			total += x;
		}
		
		System.out.println(res);
		
		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 total = 0;
		int res = 0;
		
		while(total < n) {
			
			res += t;
			total += x;
		}
		
		System.out.println(res);
		
		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 total = 0;
		int res = 0;
		
		while(total < n) {
			
			res += t;
			total += x;
		}
		
		System.out.println(res);
		
		sc.close();
	} main {
		
		Scanner sc = new Scanner(System.in);
		
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();
		
		int total = 0;
		int res = 0;
		
		while(total < n) {
			
			res += t;
			total += x;
		}
		
		System.out.println(res);
		
		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 total = 0; total 0 int res = 0; res 0 while(total < n) {
			
			res += t;
			total += x;
		} total < n total n {
			
			res += t;
			total += x;
		} res += t res t total += x total x System.out.println(res) System.out.println System.out System System.out res 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 total = 0;
		int res = 0;
		
		while(total < n) {
			
			res += t;
			total += x;
		}
		
		System.out.println(res);
		
		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 total = 0;
		int res = 0;
		
		while(total < n) {
			
			res += t;
			total += x;
		}
		
		System.out.println(res);
		
		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 total = 0;
		int res = 0;
		
		while(total < n) {
			
			res += t;
			total += x;
		}
		
		System.out.println(res);
		
		sc.close();
	}

}
