import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.math.BigInteger;
import java.util.*;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner fr = new Scanner(System.in);
        int n = fr.nextInt();
        int x = fr.nextInt();
        int xx = x;
        int t = fr.nextInt();
        int tt = t;
        if(n<x){
            System.out.println(t);
        }
        else{
            while(x<n){
                x+=xx;
                t+=tt;
            }
            System.out.println(t);
        }
    }
} import java.io.BufferedReader; BufferedReader java.io import java.io.IOException; IOException java.io import java.io.InputStreamReader; InputStreamReader java.io import java.math.BigInteger; BigInteger java.math import java.util.*; util.* java import java.util.stream.Collectors; Collectors java.util.stream import java.util.stream.Stream; Stream java.util.stream public class Main {
    public static void main(String[] args) throws Exception {
        Scanner fr = new Scanner(System.in);
        int n = fr.nextInt();
        int x = fr.nextInt();
        int xx = x;
        int t = fr.nextInt();
        int tt = t;
        if(n<x){
            System.out.println(t);
        }
        else{
            while(x<n){
                x+=xx;
                t+=tt;
            }
            System.out.println(t);
        }
    }
} Main public static void main(String[] args) throws Exception {
        Scanner fr = new Scanner(System.in);
        int n = fr.nextInt();
        int x = fr.nextInt();
        int xx = x;
        int t = fr.nextInt();
        int tt = t;
        if(n<x){
            System.out.println(t);
        }
        else{
            while(x<n){
                x+=xx;
                t+=tt;
            }
            System.out.println(t);
        }
    } main {
        Scanner fr = new Scanner(System.in);
        int n = fr.nextInt();
        int x = fr.nextInt();
        int xx = x;
        int t = fr.nextInt();
        int tt = t;
        if(n<x){
            System.out.println(t);
        }
        else{
            while(x<n){
                x+=xx;
                t+=tt;
            }
            System.out.println(t);
        }
    } Scanner fr = new Scanner(System.in); fr new Scanner(System.in) int n = fr.nextInt(); n fr.nextInt() fr.nextInt fr int x = fr.nextInt(); x fr.nextInt() fr.nextInt fr int xx = x; xx x int t = fr.nextInt(); t fr.nextInt() fr.nextInt fr int tt = t; tt t if(n<x){
            System.out.println(t);
        }
        else{
            while(x<n){
                x+=xx;
                t+=tt;
            }
            System.out.println(t);
        } n<x n x {
            System.out.println(t);
        } System.out.println(t) System.out.println System.out System System.out t {
            while(x<n){
                x+=xx;
                t+=tt;
            }
            System.out.println(t);
        } while(x<n){
                x+=xx;
                t+=tt;
            } x<n x n {
                x+=xx;
                t+=tt;
            } x+=xx x xx t+=tt t tt System.out.println(t) System.out.println System.out System System.out t String[] args args public class Main {
    public static void main(String[] args) throws Exception {
        Scanner fr = new Scanner(System.in);
        int n = fr.nextInt();
        int x = fr.nextInt();
        int xx = x;
        int t = fr.nextInt();
        int tt = t;
        if(n<x){
            System.out.println(t);
        }
        else{
            while(x<n){
                x+=xx;
                t+=tt;
            }
            System.out.println(t);
        }
    }
} public class Main {
    public static void main(String[] args) throws Exception {
        Scanner fr = new Scanner(System.in);
        int n = fr.nextInt();
        int x = fr.nextInt();
        int xx = x;
        int t = fr.nextInt();
        int tt = t;
        if(n<x){
            System.out.println(t);
        }
        else{
            while(x<n){
                x+=xx;
                t+=tt;
            }
            System.out.println(t);
        }
    }
} Main
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.math.BigInteger;
import java.util.*;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner fr = new Scanner(System.in);
        int n = fr.nextInt();
        int x = fr.nextInt();
        int xx = x;
        int t = fr.nextInt();
        int tt = t;
        if(n<x){
            System.out.println(t);
        }
        else{
            while(x<n){
                x+=xx;
                t+=tt;
            }
            System.out.println(t);
        }
    }
}
