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

public class Main {
    public static void main(String[] args) throws Exception {
        Reader sc = new Reader();
        PrintWriter pw = new PrintWriter(System.out);
        
        try {
            int n = sc.nextInt();
            int x = sc.nextInt();
            int t = sc.nextInt();
            pw.println((n+x-1)/x*t);
        }
        finally {
            pw.flush();
            pw.close();
        }
    }
    
    static class Reader {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer("");

        String next() {
            while(!st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                }
                catch(IOException io) {
                    io.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }
    }
} import java.io.*; io.* java import java.util.*; util.* java public class Main {
    public static void main(String[] args) throws Exception {
        Reader sc = new Reader();
        PrintWriter pw = new PrintWriter(System.out);
        
        try {
            int n = sc.nextInt();
            int x = sc.nextInt();
            int t = sc.nextInt();
            pw.println((n+x-1)/x*t);
        }
        finally {
            pw.flush();
            pw.close();
        }
    }
    
    static class Reader {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer("");

        String next() {
            while(!st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                }
                catch(IOException io) {
                    io.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }
    }
} Main public static void main(String[] args) throws Exception {
        Reader sc = new Reader();
        PrintWriter pw = new PrintWriter(System.out);
        
        try {
            int n = sc.nextInt();
            int x = sc.nextInt();
            int t = sc.nextInt();
            pw.println((n+x-1)/x*t);
        }
        finally {
            pw.flush();
            pw.close();
        }
    } main {
        Reader sc = new Reader();
        PrintWriter pw = new PrintWriter(System.out);
        
        try {
            int n = sc.nextInt();
            int x = sc.nextInt();
            int t = sc.nextInt();
            pw.println((n+x-1)/x*t);
        }
        finally {
            pw.flush();
            pw.close();
        }
    } Reader sc = new Reader(); sc new Reader() PrintWriter pw = new PrintWriter(System.out); pw new PrintWriter(System.out) try {
            int n = sc.nextInt();
            int x = sc.nextInt();
            int t = sc.nextInt();
            pw.println((n+x-1)/x*t);
        }
        finally {
            pw.flush();
            pw.close();
        } {
            pw.flush();
            pw.close();
        } pw.flush() pw.flush pw pw.close() pw.close pw {
            int n = sc.nextInt();
            int x = sc.nextInt();
            int t = sc.nextInt();
            pw.println((n+x-1)/x*t);
        } int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc int x = sc.nextInt(); x sc.nextInt() sc.nextInt sc int t = sc.nextInt(); t sc.nextInt() sc.nextInt sc pw.println((n+x-1)/x*t) pw.println pw (n+x-1)/x*t (n+x-1)/x (n+x-1) n+x n x 1 x t String[] args args static class Reader {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer("");

        String next() {
            while(!st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                }
                catch(IOException io) {
                    io.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }
    } Reader BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) StringTokenizer st = new StringTokenizer(""); st new StringTokenizer("") String next() {
            while(!st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                }
                catch(IOException io) {
                    io.printStackTrace();
                }
            }
            return st.nextToken();
        } next {
            while(!st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                }
                catch(IOException io) {
                    io.printStackTrace();
                }
            }
            return st.nextToken();
        } while(!st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                }
                catch(IOException io) {
                    io.printStackTrace();
                }
            } !st.hasMoreTokens() st.hasMoreTokens() st.hasMoreTokens st {
                try {
                    st = new StringTokenizer(br.readLine());
                }
                catch(IOException io) {
                    io.printStackTrace();
                }
            } try {
                    st = new StringTokenizer(br.readLine());
                }
                catch(IOException io) {
                    io.printStackTrace();
                } catch(IOException io) {
                    io.printStackTrace();
                } IOException io {
                    io.printStackTrace();
                } io.printStackTrace() io.printStackTrace io {
                    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 public class Main {
    public static void main(String[] args) throws Exception {
        Reader sc = new Reader();
        PrintWriter pw = new PrintWriter(System.out);
        
        try {
            int n = sc.nextInt();
            int x = sc.nextInt();
            int t = sc.nextInt();
            pw.println((n+x-1)/x*t);
        }
        finally {
            pw.flush();
            pw.close();
        }
    }
    
    static class Reader {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer("");

        String next() {
            while(!st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                }
                catch(IOException io) {
                    io.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }
    }
} public class Main {
    public static void main(String[] args) throws Exception {
        Reader sc = new Reader();
        PrintWriter pw = new PrintWriter(System.out);
        
        try {
            int n = sc.nextInt();
            int x = sc.nextInt();
            int t = sc.nextInt();
            pw.println((n+x-1)/x*t);
        }
        finally {
            pw.flush();
            pw.close();
        }
    }
    
    static class Reader {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer("");

        String next() {
            while(!st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                }
                catch(IOException io) {
                    io.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }
    }
} Main
import java.io.*;
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Reader sc = new Reader();
        PrintWriter pw = new PrintWriter(System.out);
        
        try {
            int n = sc.nextInt();
            int x = sc.nextInt();
            int t = sc.nextInt();
            pw.println((n+x-1)/x*t);
        }
        finally {
            pw.flush();
            pw.close();
        }
    }
    
    static class Reader {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer("");

        String next() {
            while(!st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                }
                catch(IOException io) {
                    io.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }
    }
}
