import 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 ans = 0;
        int count = 0;
        while(count<n){count+=x;
                       ans+=t;                            
                      }       
		System.out.println(ans);
	}
} import java.util.*; util.* java 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 ans = 0;
        int count = 0;
        while(count<n){count+=x;
                       ans+=t;                            
                      }       
		System.out.println(ans);
	}
} 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 ans = 0;
        int count = 0;
        while(count<n){count+=x;
                       ans+=t;                            
                      }       
		System.out.println(ans);
	} main {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();		
        int x = sc.nextInt();
		int t = sc.nextInt();
        int ans = 0;
        int count = 0;
        while(count<n){count+=x;
                       ans+=t;                            
                      }       
		System.out.println(ans);
	} 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 ans = 0; ans 0 int count = 0; count 0 while(count<n){count+=x;
                       ans+=t;                            
                      } count<n count n {count+=x;
                       ans+=t;                            
                      } count+=x count x ans+=t ans t System.out.println(ans) System.out.println System.out System System.out ans 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 ans = 0;
        int count = 0;
        while(count<n){count+=x;
                       ans+=t;                            
                      }       
		System.out.println(ans);
	}
} 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 ans = 0;
        int count = 0;
        while(count<n){count+=x;
                       ans+=t;                            
                      }       
		System.out.println(ans);
	}
} Main
import 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 ans = 0;
        int count = 0;
        while(count<n){count+=x;
                       ans+=t;                            
                      }       
		System.out.println(ans);
	}
}