//package Div2_655;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

public class Main {
    public static void main(String[] args)throws IOException {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st=new StringTokenizer(br.readLine());
        int n=Integer.parseInt(st.nextToken());
        int x=Integer.parseInt(st.nextToken());
        int t=Integer.parseInt(st.nextToken());
        int ans=n/x;
        if(n%x!=0){
            ans++;
        }
        ans*=t;
        System.out.println(ans);
    }
} import java.io.BufferedReader; BufferedReader java.io import java.io.IOException; IOException java.io import java.io.InputStreamReader; InputStreamReader java.io import java.util.StringTokenizer; StringTokenizer java.util public class Main {
    public static void main(String[] args)throws IOException {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st=new StringTokenizer(br.readLine());
        int n=Integer.parseInt(st.nextToken());
        int x=Integer.parseInt(st.nextToken());
        int t=Integer.parseInt(st.nextToken());
        int ans=n/x;
        if(n%x!=0){
            ans++;
        }
        ans*=t;
        System.out.println(ans);
    }
} Main public static void main(String[] args)throws IOException {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st=new StringTokenizer(br.readLine());
        int n=Integer.parseInt(st.nextToken());
        int x=Integer.parseInt(st.nextToken());
        int t=Integer.parseInt(st.nextToken());
        int ans=n/x;
        if(n%x!=0){
            ans++;
        }
        ans*=t;
        System.out.println(ans);
    } main {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st=new StringTokenizer(br.readLine());
        int n=Integer.parseInt(st.nextToken());
        int x=Integer.parseInt(st.nextToken());
        int t=Integer.parseInt(st.nextToken());
        int ans=n/x;
        if(n%x!=0){
            ans++;
        }
        ans*=t;
        System.out.println(ans);
    } BufferedReader br=new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) StringTokenizer st=new StringTokenizer(br.readLine()); st new StringTokenizer(br.readLine()) int n=Integer.parseInt(st.nextToken()); n Integer.parseInt(st.nextToken()) Integer.parseInt Integer st.nextToken() st.nextToken st int x=Integer.parseInt(st.nextToken()); x Integer.parseInt(st.nextToken()) Integer.parseInt Integer st.nextToken() st.nextToken st int t=Integer.parseInt(st.nextToken()); t Integer.parseInt(st.nextToken()) Integer.parseInt Integer st.nextToken() st.nextToken st int ans=n/x; ans n/x n x if(n%x!=0){
            ans++;
        } n%x!=0 n%x n x 0 {
            ans++;
        } ans++ ans 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)throws IOException {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st=new StringTokenizer(br.readLine());
        int n=Integer.parseInt(st.nextToken());
        int x=Integer.parseInt(st.nextToken());
        int t=Integer.parseInt(st.nextToken());
        int ans=n/x;
        if(n%x!=0){
            ans++;
        }
        ans*=t;
        System.out.println(ans);
    }
} public class Main {
    public static void main(String[] args)throws IOException {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st=new StringTokenizer(br.readLine());
        int n=Integer.parseInt(st.nextToken());
        int x=Integer.parseInt(st.nextToken());
        int t=Integer.parseInt(st.nextToken());
        int ans=n/x;
        if(n%x!=0){
            ans++;
        }
        ans*=t;
        System.out.println(ans);
    }
} Main
//package Div2_655;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

public class Main {
    public static void main(String[] args)throws IOException {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st=new StringTokenizer(br.readLine());
        int n=Integer.parseInt(st.nextToken());
        int x=Integer.parseInt(st.nextToken());
        int t=Integer.parseInt(st.nextToken());
        int ans=n/x;
        if(n%x!=0){
            ans++;
        }
        ans*=t;
        System.out.println(ans);
    }
}
