import java.io.BufferedReader;
import java.io.*;
import java.util.*;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Collections;
import java.util.Arrays;

public class Main {
	public static void main(final String[] args){
    
    final Scanner sc = new Scanner(System.in);
    //final List<Long> list = new ArrayList<>();
    //final List<Long> list2 = new ArrayList<>();

    int n = sc.nextInt();
    int x = sc.nextInt();
    int t = sc.nextInt();

    int a = n / x ;
    if(n % x == 0){
        System.out.println(n / x * t);
    }else{
        System.out.println((n / x + 1) * t);
    }

    





}
} import java.io.BufferedReader; BufferedReader java.io import java.io.*; io.* java import java.util.*; util.* java import java.util.ArrayList; ArrayList java.util import java.util.Iterator; Iterator java.util import java.util.List; List java.util import java.util.Collections; Collections java.util import java.util.Arrays; Arrays java.util public class Main {
	public static void main(final String[] args){
    
    final Scanner sc = new Scanner(System.in);
    //final List<Long> list = new ArrayList<>();
    //final List<Long> list2 = new ArrayList<>();

    int n = sc.nextInt();
    int x = sc.nextInt();
    int t = sc.nextInt();

    int a = n / x ;
    if(n % x == 0){
        System.out.println(n / x * t);
    }else{
        System.out.println((n / x + 1) * t);
    }

    





}
} Main public static void main(final String[] args){
    
    final Scanner sc = new Scanner(System.in);
    //final List<Long> list = new ArrayList<>();
    //final List<Long> list2 = new ArrayList<>();

    int n = sc.nextInt();
    int x = sc.nextInt();
    int t = sc.nextInt();

    int a = n / x ;
    if(n % x == 0){
        System.out.println(n / x * t);
    }else{
        System.out.println((n / x + 1) * t);
    }

    





} main {
    
    final Scanner sc = new Scanner(System.in);
    //final List<Long> list = new ArrayList<>();
    //final List<Long> list2 = new ArrayList<>();

    int n = sc.nextInt();
    int x = sc.nextInt();
    int t = sc.nextInt();

    int a = n / x ;
    if(n % x == 0){
        System.out.println(n / x * t);
    }else{
        System.out.println((n / x + 1) * t);
    }

    





} final 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 a = n / x ; a n / x n x if(n % x == 0){
        System.out.println(n / x * t);
    }else{
        System.out.println((n / x + 1) * t);
    } n % x == 0 n % x n x 0 {
        System.out.println(n / x * t);
    } System.out.println(n / x * t) System.out.println System.out System System.out n / x * t n / x n x t {
        System.out.println((n / x + 1) * t);
    } System.out.println((n / x + 1) * t) System.out.println System.out System System.out (n / x + 1) * t (n / x + 1) n / x n x 1 t final String[] args args public class Main {
	public static void main(final String[] args){
    
    final Scanner sc = new Scanner(System.in);
    //final List<Long> list = new ArrayList<>();
    //final List<Long> list2 = new ArrayList<>();

    int n = sc.nextInt();
    int x = sc.nextInt();
    int t = sc.nextInt();

    int a = n / x ;
    if(n % x == 0){
        System.out.println(n / x * t);
    }else{
        System.out.println((n / x + 1) * t);
    }

    





}
} public class Main {
	public static void main(final String[] args){
    
    final Scanner sc = new Scanner(System.in);
    //final List<Long> list = new ArrayList<>();
    //final List<Long> list2 = new ArrayList<>();

    int n = sc.nextInt();
    int x = sc.nextInt();
    int t = sc.nextInt();

    int a = n / x ;
    if(n % x == 0){
        System.out.println(n / x * t);
    }else{
        System.out.println((n / x + 1) * t);
    }

    





}
} Main
import java.io.BufferedReader;
import java.io.*;
import java.util.*;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Collections;
import java.util.Arrays;

public class Main {
	public static void main(final String[] args){
    
    final Scanner sc = new Scanner(System.in);
    //final List<Long> list = new ArrayList<>();
    //final List<Long> list2 = new ArrayList<>();

    int n = sc.nextInt();
    int x = sc.nextInt();
    int t = sc.nextInt();

    int a = n / x ;
    if(n % x == 0){
        System.out.println(n / x * t);
    }else{
        System.out.println((n / x + 1) * t);
    }

    





}
}