import java.util.*;
public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();
		
		double N=n;
		double X=x;
		double T=t;
		
		 double res=0.0;
		if(N<X)
			res=T;
		else
		{
			res=Math.ceil(N/X);
			res=res*T;
		}
		System.out.println((int)res);
	}

} import java.util.*; util.* java public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();
		
		double N=n;
		double X=x;
		double T=t;
		
		 double res=0.0;
		if(N<X)
			res=T;
		else
		{
			res=Math.ceil(N/X);
			res=res*T;
		}
		System.out.println((int)res);
	}

} Main public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();
		
		double N=n;
		double X=x;
		double T=t;
		
		 double res=0.0;
		if(N<X)
			res=T;
		else
		{
			res=Math.ceil(N/X);
			res=res*T;
		}
		System.out.println((int)res);
	} main {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();
		
		double N=n;
		double X=x;
		double T=t;
		
		 double res=0.0;
		if(N<X)
			res=T;
		else
		{
			res=Math.ceil(N/X);
			res=res*T;
		}
		System.out.println((int)res);
	} 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 double N=n; N n double X=x; X x double T=t; T t double res=0.0; res 0.0 if(N<X)
			res=T;
		else
		{
			res=Math.ceil(N/X);
			res=res*T;
		} N<X N X res=T res T {
			res=Math.ceil(N/X);
			res=res*T;
		} res=Math.ceil(N/X) res Math.ceil(N/X) Math.ceil Math N/X N X res=res*T res res*T res T System.out.println((int)res) System.out.println System.out System System.out (int)res String[] args args public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();
		
		double N=n;
		double X=x;
		double T=t;
		
		 double res=0.0;
		if(N<X)
			res=T;
		else
		{
			res=Math.ceil(N/X);
			res=res*T;
		}
		System.out.println((int)res);
	}

} public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();
		
		double N=n;
		double X=x;
		double T=t;
		
		 double res=0.0;
		if(N<X)
			res=T;
		else
		{
			res=Math.ceil(N/X);
			res=res*T;
		}
		System.out.println((int)res);
	}

} Main
import java.util.*;
public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();
		
		double N=n;
		double X=x;
		double T=t;
		
		 double res=0.0;
		if(N<X)
			res=T;
		else
		{
			res=Math.ceil(N/X);
			res=res*T;
		}
		System.out.println((int)res);
	}

}