import java.util.Scanner;
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 time=t;
		int x1=x;
		while(x<n)
		{
			t=t+time;
			x=x+x1;
		}
		System.out.println(t);
		
		sc.close();		
	}

} import java.util.Scanner; Scanner java.util 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 time=t;
		int x1=x;
		while(x<n)
		{
			t=t+time;
			x=x+x1;
		}
		System.out.println(t);
		
		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 time=t;
		int x1=x;
		while(x<n)
		{
			t=t+time;
			x=x+x1;
		}
		System.out.println(t);
		
		sc.close();		
	} main {
		Scanner sc=new Scanner(System.in);
		int n=sc.nextInt();
		int x=sc.nextInt();
		int t=sc.nextInt();
		int time=t;
		int x1=x;
		while(x<n)
		{
			t=t+time;
			x=x+x1;
		}
		System.out.println(t);
		
		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 time=t; time t int x1=x; x1 x while(x<n)
		{
			t=t+time;
			x=x+x1;
		} x<n x n {
			t=t+time;
			x=x+x1;
		} t=t+time t t+time t time x=x+x1 x x+x1 x x1 System.out.println(t) System.out.println System.out System System.out t sc.close() sc.close sc String[] args args
import java.util.Scanner;
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 time=t;
		int x1=x;
		while(x<n)
		{
			t=t+time;
			x=x+x1;
		}
		System.out.println(t);
		
		sc.close();		
	}

}
