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());
        }
    }
}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz