// package Contest#176;
import java.util.*;
import java.io.*;

public class Main {
    public static void main(String[] args) throws Exception{
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(System.out);

        StringTokenizer st = new StringTokenizer(br.readLine());
        int n = Integer.parseInt(st.nextToken());
        int x = Integer.parseInt(st.nextToken());
        int t = Integer.parseInt(st.nextToken());

        // out.println(n / x);
        int time = (int) Math.ceil(1.0 * n / x);
        out.println(time * t);
        out.close();
    }
} import java.util.*; util.* java import java.io.*; io.* java public class Main {
    public static void main(String[] args) throws Exception{
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(System.out);

        StringTokenizer st = new StringTokenizer(br.readLine());
        int n = Integer.parseInt(st.nextToken());
        int x = Integer.parseInt(st.nextToken());
        int t = Integer.parseInt(st.nextToken());

        // out.println(n / x);
        int time = (int) Math.ceil(1.0 * n / x);
        out.println(time * t);
        out.close();
    }
} Main public static void main(String[] args) throws Exception{
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(System.out);

        StringTokenizer st = new StringTokenizer(br.readLine());
        int n = Integer.parseInt(st.nextToken());
        int x = Integer.parseInt(st.nextToken());
        int t = Integer.parseInt(st.nextToken());

        // out.println(n / x);
        int time = (int) Math.ceil(1.0 * n / x);
        out.println(time * t);
        out.close();
    } main {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(System.out);

        StringTokenizer st = new StringTokenizer(br.readLine());
        int n = Integer.parseInt(st.nextToken());
        int x = Integer.parseInt(st.nextToken());
        int t = Integer.parseInt(st.nextToken());

        // out.println(n / x);
        int time = (int) Math.ceil(1.0 * n / x);
        out.println(time * t);
        out.close();
    } BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) PrintWriter out = new PrintWriter(System.out); out new PrintWriter(System.out) 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 time = (int) Math.ceil(1.0 * n / x); time (int) Math.ceil(1.0 * n / x) Math.ceil Math 1.0 * n / x 1.0 * n 1.0 n x out.println(time * t) out.println out time * t time t out.close() out.close out String[] args args public class Main {
    public static void main(String[] args) throws Exception{
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(System.out);

        StringTokenizer st = new StringTokenizer(br.readLine());
        int n = Integer.parseInt(st.nextToken());
        int x = Integer.parseInt(st.nextToken());
        int t = Integer.parseInt(st.nextToken());

        // out.println(n / x);
        int time = (int) Math.ceil(1.0 * n / x);
        out.println(time * t);
        out.close();
    }
} public class Main {
    public static void main(String[] args) throws Exception{
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(System.out);

        StringTokenizer st = new StringTokenizer(br.readLine());
        int n = Integer.parseInt(st.nextToken());
        int x = Integer.parseInt(st.nextToken());
        int t = Integer.parseInt(st.nextToken());

        // out.println(n / x);
        int time = (int) Math.ceil(1.0 * n / x);
        out.println(time * t);
        out.close();
    }
} Main
// package Contest#176;
import java.util.*;
import java.io.*;

public class Main {
    public static void main(String[] args) throws Exception{
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(System.out);

        StringTokenizer st = new StringTokenizer(br.readLine());
        int n = Integer.parseInt(st.nextToken());
        int x = Integer.parseInt(st.nextToken());
        int t = Integer.parseInt(st.nextToken());

        // out.println(n / x);
        int time = (int) Math.ceil(1.0 * n / x);
        out.println(time * t);
        out.close();
    }
}