import java.util.Scanner;

public class Main {
    static Scanner sc = new Scanner(System.in);
    static final int mod = 1000000007;

    public static void main(String[] args) {

        int  n = sc.nextInt();
         int x = sc.nextInt();
         int t = sc.nextInt();
         
         int ans = t*(n/x);
         if(n%x!=0)
         ans+= t;
         System.out.println(ans);




    }
















    static int max(int a, int b)
    {
        return Math.max(a,b);
    }
    static int max(int a, int b, int c)
    {
        return Math.max(max(a,b), c);
    }
    static int max(int a, int b, int c, int d)
    {
        return Math.max(max(a,b), max(c,d));
    }

    static int min(int a, int b)
    {
        return Math.min(a, b);
    }

    static int min(int a, int b, int c )
    {
        return Math.min(a, min(b,c));
    }

    static int min(int a, int b, int c, int d )
    {
        return Math.min(min(a,d), min(b,c));
    }

    static boolean isPower(int a, int b)
    {
        double temp = Math.log(a)/Math.log(b);
        return temp == (int) temp;
    }
    static boolean isPrime(int n)
    {
        if(n==1) return false;
        if(n==2) return true;
        if(n%2==0) return false;

        if(n<9)return true;
        if(n%3==0) return false;

        int r = (int)Math.sqrt(n);

        for(int i = 5; i<=r; i +=6)
        {
            if(n%i==0) return false;
            if(n%(i+2)==0) return false;
        }
        return true;



    }
}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz