import java.util.*;

public class Main {
	public static void main(String args[]) {
		
		Scanner ob = new Scanner(System.in);
		int N = ob.nextInt();
		int X = ob.nextInt();
		int T = ob.nextInt();
		int result = 0;
		
		while(N > 0) {
			N -= X;
			result += T;
		}
		System.out.println(result);
		ob.close();
	}
} import java.util.*; util.* java public class Main {
	public static void main(String args[]) {
		
		Scanner ob = new Scanner(System.in);
		int N = ob.nextInt();
		int X = ob.nextInt();
		int T = ob.nextInt();
		int result = 0;
		
		while(N > 0) {
			N -= X;
			result += T;
		}
		System.out.println(result);
		ob.close();
	}
} Main public static void main(String args[]) {
		
		Scanner ob = new Scanner(System.in);
		int N = ob.nextInt();
		int X = ob.nextInt();
		int T = ob.nextInt();
		int result = 0;
		
		while(N > 0) {
			N -= X;
			result += T;
		}
		System.out.println(result);
		ob.close();
	} main {
		
		Scanner ob = new Scanner(System.in);
		int N = ob.nextInt();
		int X = ob.nextInt();
		int T = ob.nextInt();
		int result = 0;
		
		while(N > 0) {
			N -= X;
			result += T;
		}
		System.out.println(result);
		ob.close();
	} Scanner ob = new Scanner(System.in); ob new Scanner(System.in) int N = ob.nextInt(); N ob.nextInt() ob.nextInt ob int X = ob.nextInt(); X ob.nextInt() ob.nextInt ob int T = ob.nextInt(); T ob.nextInt() ob.nextInt ob int result = 0; result 0 while(N > 0) {
			N -= X;
			result += T;
		} N > 0 N 0 {
			N -= X;
			result += T;
		} N -= X N X result += T result T System.out.println(result) System.out.println System.out System System.out result ob.close() ob.close ob String args[] args public class Main {
	public static void main(String args[]) {
		
		Scanner ob = new Scanner(System.in);
		int N = ob.nextInt();
		int X = ob.nextInt();
		int T = ob.nextInt();
		int result = 0;
		
		while(N > 0) {
			N -= X;
			result += T;
		}
		System.out.println(result);
		ob.close();
	}
} public class Main {
	public static void main(String args[]) {
		
		Scanner ob = new Scanner(System.in);
		int N = ob.nextInt();
		int X = ob.nextInt();
		int T = ob.nextInt();
		int result = 0;
		
		while(N > 0) {
			N -= X;
			result += T;
		}
		System.out.println(result);
		ob.close();
	}
} Main
import java.util.*;

public class Main {
	public static void main(String args[]) {
		
		Scanner ob = new Scanner(System.in);
		int N = ob.nextInt();
		int X = ob.nextInt();
		int T = ob.nextInt();
		int result = 0;
		
		while(N > 0) {
			N -= X;
			result += T;
		}
		System.out.println(result);
		ob.close();
	}
}
