import java.io.*;
import java.util.*;

import static java.lang.Integer.*;

public class Main {

    public static void main(String[] args) throws IOException {
        PrintWriter prnt = new PrintWriter(System.out);
        BufferedReader read = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(read.readLine());
        int N = parseInt(st.nextToken()), X = parseInt(st.nextToken()), T = parseInt(st.nextToken());
        int D = N / X;
        if (N % X != 0) {
            D += 1;
        }
        prnt.println(D * T);
        prnt.close();
    }
} import java.io.*; io.* java import java.util.*; util.* java import static java.lang.Integer.*; import static java.lang.Integer.*; import static java.lang.Integer.*; public class Main {

    public static void main(String[] args) throws IOException {
        PrintWriter prnt = new PrintWriter(System.out);
        BufferedReader read = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(read.readLine());
        int N = parseInt(st.nextToken()), X = parseInt(st.nextToken()), T = parseInt(st.nextToken());
        int D = N / X;
        if (N % X != 0) {
            D += 1;
        }
        prnt.println(D * T);
        prnt.close();
    }
} Main public static void main(String[] args) throws IOException {
        PrintWriter prnt = new PrintWriter(System.out);
        BufferedReader read = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(read.readLine());
        int N = parseInt(st.nextToken()), X = parseInt(st.nextToken()), T = parseInt(st.nextToken());
        int D = N / X;
        if (N % X != 0) {
            D += 1;
        }
        prnt.println(D * T);
        prnt.close();
    } main {
        PrintWriter prnt = new PrintWriter(System.out);
        BufferedReader read = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(read.readLine());
        int N = parseInt(st.nextToken()), X = parseInt(st.nextToken()), T = parseInt(st.nextToken());
        int D = N / X;
        if (N % X != 0) {
            D += 1;
        }
        prnt.println(D * T);
        prnt.close();
    } PrintWriter prnt = new PrintWriter(System.out); prnt new PrintWriter(System.out) BufferedReader read = new BufferedReader(new InputStreamReader(System.in)); read new BufferedReader(new InputStreamReader(System.in)) StringTokenizer st = new StringTokenizer(read.readLine()); st new StringTokenizer(read.readLine()) int N = parseInt(st.nextToken()) N parseInt(st.nextToken()) parseInt st.nextToken() st.nextToken st X = parseInt(st.nextToken()) X parseInt(st.nextToken()) parseInt st.nextToken() st.nextToken st T = parseInt(st.nextToken()); T parseInt(st.nextToken()) parseInt st.nextToken() st.nextToken st int D = N / X; D N / X N X if (N % X != 0) {
            D += 1;
        } N % X != 0 N % X N X 0 {
            D += 1;
        } D += 1 D 1 prnt.println(D * T) prnt.println prnt D * T D T prnt.close() prnt.close prnt String[] args args public class Main {

    public static void main(String[] args) throws IOException {
        PrintWriter prnt = new PrintWriter(System.out);
        BufferedReader read = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(read.readLine());
        int N = parseInt(st.nextToken()), X = parseInt(st.nextToken()), T = parseInt(st.nextToken());
        int D = N / X;
        if (N % X != 0) {
            D += 1;
        }
        prnt.println(D * T);
        prnt.close();
    }
} public class Main {

    public static void main(String[] args) throws IOException {
        PrintWriter prnt = new PrintWriter(System.out);
        BufferedReader read = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(read.readLine());
        int N = parseInt(st.nextToken()), X = parseInt(st.nextToken()), T = parseInt(st.nextToken());
        int D = N / X;
        if (N % X != 0) {
            D += 1;
        }
        prnt.println(D * T);
        prnt.close();
    }
} Main
import java.io.*;
import java.util.*;

import static java.lang.Integer.*;

public class Main {

    public static void main(String[] args) throws IOException {
        PrintWriter prnt = new PrintWriter(System.out);
        BufferedReader read = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(read.readLine());
        int N = parseInt(st.nextToken()), X = parseInt(st.nextToken()), T = parseInt(st.nextToken());
        int D = N / X;
        if (N % X != 0) {
            D += 1;
        }
        prnt.println(D * T);
        prnt.close();
    }
}