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

public class Main {
    public static void main(final String[] args) {
        final FastReader s=new FastReader();
        int n = s.nextInt();
        int x = s.nextInt();
        int t = s.nextInt();
        int res = (n/x)*t;
        if(n%x!=0) res+=t;

        System.out.println(res);
    }

    static class FastReader
    {
        BufferedReader br;
        StringTokenizer st;
        public FastReader() { br = new BufferedReader(new InputStreamReader(System.in)); }
        String next() {
            while (st == null || !st.hasMoreElements()) {
                try { st = new StringTokenizer(br.readLine()); }
                catch (final IOException  e) { e.printStackTrace(); }
            }
            return st.nextToken();
        }
        int nextInt() { return Integer.parseInt(next()); }
        long nextLong() { return Long.parseLong(next()); }
        double nextDouble() { return Double.parseDouble(next()); }
        String nextLine() {
            String str = "";
            try { str = br.readLine(); }
            catch (final IOException e) { e.printStackTrace(); }
            return str;
        }
    }
} import java.io.*; io.* java import java.util.*; util.* java public class Main {
    public static void main(final String[] args) {
        final FastReader s=new FastReader();
        int n = s.nextInt();
        int x = s.nextInt();
        int t = s.nextInt();
        int res = (n/x)*t;
        if(n%x!=0) res+=t;

        System.out.println(res);
    }

    static class FastReader
    {
        BufferedReader br;
        StringTokenizer st;
        public FastReader() { br = new BufferedReader(new InputStreamReader(System.in)); }
        String next() {
            while (st == null || !st.hasMoreElements()) {
                try { st = new StringTokenizer(br.readLine()); }
                catch (final IOException  e) { e.printStackTrace(); }
            }
            return st.nextToken();
        }
        int nextInt() { return Integer.parseInt(next()); }
        long nextLong() { return Long.parseLong(next()); }
        double nextDouble() { return Double.parseDouble(next()); }
        String nextLine() {
            String str = "";
            try { str = br.readLine(); }
            catch (final IOException e) { e.printStackTrace(); }
            return str;
        }
    }
} Main public static void main(final String[] args) {
        final FastReader s=new FastReader();
        int n = s.nextInt();
        int x = s.nextInt();
        int t = s.nextInt();
        int res = (n/x)*t;
        if(n%x!=0) res+=t;

        System.out.println(res);
    } main {
        final FastReader s=new FastReader();
        int n = s.nextInt();
        int x = s.nextInt();
        int t = s.nextInt();
        int res = (n/x)*t;
        if(n%x!=0) res+=t;

        System.out.println(res);
    } final FastReader s=new FastReader(); s new FastReader() int n = s.nextInt(); n s.nextInt() s.nextInt s int x = s.nextInt(); x s.nextInt() s.nextInt s int t = s.nextInt(); t s.nextInt() s.nextInt s int res = (n/x)*t; res (n/x)*t (n/x) n x t if(n%x!=0) res+=t; n%x!=0 n%x n x 0 res+=t res t System.out.println(res) System.out.println System.out System System.out res final String[] args args static class FastReader
    {
        BufferedReader br;
        StringTokenizer st;
        public FastReader() { br = new BufferedReader(new InputStreamReader(System.in)); }
        String next() {
            while (st == null || !st.hasMoreElements()) {
                try { st = new StringTokenizer(br.readLine()); }
                catch (final IOException  e) { e.printStackTrace(); }
            }
            return st.nextToken();
        }
        int nextInt() { return Integer.parseInt(next()); }
        long nextLong() { return Long.parseLong(next()); }
        double nextDouble() { return Double.parseDouble(next()); }
        String nextLine() {
            String str = "";
            try { str = br.readLine(); }
            catch (final IOException e) { e.printStackTrace(); }
            return str;
        }
    } FastReader BufferedReader br; br StringTokenizer st; st public FastReader() { br = new BufferedReader(new InputStreamReader(System.in)); } FastReader { br = new BufferedReader(new InputStreamReader(System.in)); } br = new BufferedReader(new InputStreamReader(System.in)) br new BufferedReader(new InputStreamReader(System.in)) String next() {
            while (st == null || !st.hasMoreElements()) {
                try { st = new StringTokenizer(br.readLine()); }
                catch (final IOException  e) { e.printStackTrace(); }
            }
            return st.nextToken();
        } next {
            while (st == null || !st.hasMoreElements()) {
                try { st = new StringTokenizer(br.readLine()); }
                catch (final IOException  e) { e.printStackTrace(); }
            }
            return st.nextToken();
        } while (st == null || !st.hasMoreElements()) {
                try { st = new StringTokenizer(br.readLine()); }
                catch (final IOException  e) { e.printStackTrace(); }
            } st == null || !st.hasMoreElements() st == null st null !st.hasMoreElements() st.hasMoreElements() st.hasMoreElements st {
                try { st = new StringTokenizer(br.readLine()); }
                catch (final IOException  e) { e.printStackTrace(); }
            } try { st = new StringTokenizer(br.readLine()); }
                catch (final IOException  e) { e.printStackTrace(); } catch (final IOException  e) { e.printStackTrace(); } final IOException  e { e.printStackTrace(); } e.printStackTrace() e.printStackTrace e { st = new StringTokenizer(br.readLine()); } st = new StringTokenizer(br.readLine()) st new StringTokenizer(br.readLine()) return st.nextToken(); st.nextToken() st.nextToken st int nextInt() { return Integer.parseInt(next()); } nextInt { return Integer.parseInt(next()); } return Integer.parseInt(next()); Integer.parseInt(next()) Integer.parseInt Integer next() next long nextLong() { return Long.parseLong(next()); } nextLong { return Long.parseLong(next()); } return Long.parseLong(next()); Long.parseLong(next()) Long.parseLong Long next() next double nextDouble() { return Double.parseDouble(next()); } nextDouble { return Double.parseDouble(next()); } return Double.parseDouble(next()); Double.parseDouble(next()) Double.parseDouble Double next() next String nextLine() {
            String str = "";
            try { str = br.readLine(); }
            catch (final IOException e) { e.printStackTrace(); }
            return str;
        } nextLine {
            String str = "";
            try { str = br.readLine(); }
            catch (final IOException e) { e.printStackTrace(); }
            return str;
        } String str = ""; str "" try { str = br.readLine(); }
            catch (final IOException e) { e.printStackTrace(); } catch (final IOException e) { e.printStackTrace(); } final IOException e { e.printStackTrace(); } e.printStackTrace() e.printStackTrace e { str = br.readLine(); } str = br.readLine() str br.readLine() br.readLine br return str; str public class Main {
    public static void main(final String[] args) {
        final FastReader s=new FastReader();
        int n = s.nextInt();
        int x = s.nextInt();
        int t = s.nextInt();
        int res = (n/x)*t;
        if(n%x!=0) res+=t;

        System.out.println(res);
    }

    static class FastReader
    {
        BufferedReader br;
        StringTokenizer st;
        public FastReader() { br = new BufferedReader(new InputStreamReader(System.in)); }
        String next() {
            while (st == null || !st.hasMoreElements()) {
                try { st = new StringTokenizer(br.readLine()); }
                catch (final IOException  e) { e.printStackTrace(); }
            }
            return st.nextToken();
        }
        int nextInt() { return Integer.parseInt(next()); }
        long nextLong() { return Long.parseLong(next()); }
        double nextDouble() { return Double.parseDouble(next()); }
        String nextLine() {
            String str = "";
            try { str = br.readLine(); }
            catch (final IOException e) { e.printStackTrace(); }
            return str;
        }
    }
} public class Main {
    public static void main(final String[] args) {
        final FastReader s=new FastReader();
        int n = s.nextInt();
        int x = s.nextInt();
        int t = s.nextInt();
        int res = (n/x)*t;
        if(n%x!=0) res+=t;

        System.out.println(res);
    }

    static class FastReader
    {
        BufferedReader br;
        StringTokenizer st;
        public FastReader() { br = new BufferedReader(new InputStreamReader(System.in)); }
        String next() {
            while (st == null || !st.hasMoreElements()) {
                try { st = new StringTokenizer(br.readLine()); }
                catch (final IOException  e) { e.printStackTrace(); }
            }
            return st.nextToken();
        }
        int nextInt() { return Integer.parseInt(next()); }
        long nextLong() { return Long.parseLong(next()); }
        double nextDouble() { return Double.parseDouble(next()); }
        String nextLine() {
            String str = "";
            try { str = br.readLine(); }
            catch (final IOException e) { e.printStackTrace(); }
            return str;
        }
    }
} Main
import java.io.*;
import java.util.*;

public class Main {
    public static void main(final String[] args) {
        final FastReader s=new FastReader();
        int n = s.nextInt();
        int x = s.nextInt();
        int t = s.nextInt();
        int res = (n/x)*t;
        if(n%x!=0) res+=t;

        System.out.println(res);
    }

    static class FastReader
    {
        BufferedReader br;
        StringTokenizer st;
        public FastReader() { br = new BufferedReader(new InputStreamReader(System.in)); }
        String next() {
            while (st == null || !st.hasMoreElements()) {
                try { st = new StringTokenizer(br.readLine()); }
                catch (final IOException  e) { e.printStackTrace(); }
            }
            return st.nextToken();
        }
        int nextInt() { return Integer.parseInt(next()); }
        long nextLong() { return Long.parseLong(next()); }
        double nextDouble() { return Double.parseDouble(next()); }
        String nextLine() {
            String str = "";
            try { str = br.readLine(); }
            catch (final IOException e) { e.printStackTrace(); }
            return str;
        }
    }
}