import java.util.*;
class Main
{
	public static void main(String []args)
	{
		Scanner scan = new Scanner(System.in);
		int N,X,T;
		N = scan.nextInt();
		X = scan.nextInt();
		T = scan.nextInt();
		
		int count  = N/X;
		
		if(N%X == 0)
		{
			System.out.print(count*T);
		}
		else
		{
			System.out.print((count+1)*T);
		}
	}
} import java.util.*; util.* java class Main
{
	public static void main(String []args)
	{
		Scanner scan = new Scanner(System.in);
		int N,X,T;
		N = scan.nextInt();
		X = scan.nextInt();
		T = scan.nextInt();
		
		int count  = N/X;
		
		if(N%X == 0)
		{
			System.out.print(count*T);
		}
		else
		{
			System.out.print((count+1)*T);
		}
	}
} Main public static void main(String []args)
	{
		Scanner scan = new Scanner(System.in);
		int N,X,T;
		N = scan.nextInt();
		X = scan.nextInt();
		T = scan.nextInt();
		
		int count  = N/X;
		
		if(N%X == 0)
		{
			System.out.print(count*T);
		}
		else
		{
			System.out.print((count+1)*T);
		}
	} main {
		Scanner scan = new Scanner(System.in);
		int N,X,T;
		N = scan.nextInt();
		X = scan.nextInt();
		T = scan.nextInt();
		
		int count  = N/X;
		
		if(N%X == 0)
		{
			System.out.print(count*T);
		}
		else
		{
			System.out.print((count+1)*T);
		}
	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int N N X X T; T N = scan.nextInt() N scan.nextInt() scan.nextInt scan X = scan.nextInt() X scan.nextInt() scan.nextInt scan T = scan.nextInt() T scan.nextInt() scan.nextInt scan int count  = N/X; count N/X N X if(N%X == 0)
		{
			System.out.print(count*T);
		}
		else
		{
			System.out.print((count+1)*T);
		} N%X == 0 N%X N X 0 {
			System.out.print(count*T);
		} System.out.print(count*T) System.out.print System.out System System.out count*T count T {
			System.out.print((count+1)*T);
		} System.out.print((count+1)*T) System.out.print System.out System System.out (count+1)*T (count+1) count 1 T String []args args
import java.util.*;
class Main
{
	public static void main(String []args)
	{
		Scanner scan = new Scanner(System.in);
		int N,X,T;
		N = scan.nextInt();
		X = scan.nextInt();
		T = scan.nextInt();
		
		int count  = N/X;
		
		if(N%X == 0)
		{
			System.out.print(count*T);
		}
		else
		{
			System.out.print((count+1)*T);
		}
	}
}