import java.util.*;

public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long n = sc.nextLong();
        long x = sc.nextLong();
        long t = sc.nextLong();
        long result = (n / x) * t;
        if(n % x != 0) {
            result += t;
        }
        System.out.println(result);
    }
} import java.util.*; util.* java public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long n = sc.nextLong();
        long x = sc.nextLong();
        long t = sc.nextLong();
        long result = (n / x) * t;
        if(n % x != 0) {
            result += t;
        }
        System.out.println(result);
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long n = sc.nextLong();
        long x = sc.nextLong();
        long t = sc.nextLong();
        long result = (n / x) * t;
        if(n % x != 0) {
            result += t;
        }
        System.out.println(result);
    } main {
        Scanner sc = new Scanner(System.in);
        long n = sc.nextLong();
        long x = sc.nextLong();
        long t = sc.nextLong();
        long result = (n / x) * t;
        if(n % x != 0) {
            result += t;
        }
        System.out.println(result);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) long n = sc.nextLong(); n sc.nextLong() sc.nextLong sc long x = sc.nextLong(); x sc.nextLong() sc.nextLong sc long t = sc.nextLong(); t sc.nextLong() sc.nextLong sc long result = (n / x) * t; result (n / x) * t (n / x) n x t if(n % x != 0) {
            result += t;
        } n % x != 0 n % x n x 0 {
            result += t;
        } result += t result t System.out.println(result) System.out.println System.out System System.out result String[] args args public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long n = sc.nextLong();
        long x = sc.nextLong();
        long t = sc.nextLong();
        long result = (n / x) * t;
        if(n % x != 0) {
            result += t;
        }
        System.out.println(result);
    }
} public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long n = sc.nextLong();
        long x = sc.nextLong();
        long t = sc.nextLong();
        long result = (n / x) * t;
        if(n % x != 0) {
            result += t;
        }
        System.out.println(result);
    }
} Main
import java.util.*;

public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long n = sc.nextLong();
        long x = sc.nextLong();
        long t = sc.nextLong();
        long result = (n / x) * t;
        if(n % x != 0) {
            result += t;
        }
        System.out.println(result);
    }
}