import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.regex.*;

public class Main {


    public static void main(String[] args) throws IOException {
    
    	Scanner scan = new Scanner(System.in);
    	
    	
    	int n = scan.nextInt();
    	int x = scan.nextInt();
    	int t = scan.nextInt();
    	
    	
    	int time = 0;
    	
    	while (n > 0) {
    		n -= x;
    		time += t;
    	}
    
    	System.out.println(time);
    	
    	
    	
    	
    	}
} import java.io.*; io.* java import java.math.*; math.* java import java.security.*; security.* java import java.text.*; text.* java import java.util.*; util.* java import java.util.concurrent.*; concurrent.* java.util import java.util.regex.*; regex.* java.util public class Main {


    public static void main(String[] args) throws IOException {
    
    	Scanner scan = new Scanner(System.in);
    	
    	
    	int n = scan.nextInt();
    	int x = scan.nextInt();
    	int t = scan.nextInt();
    	
    	
    	int time = 0;
    	
    	while (n > 0) {
    		n -= x;
    		time += t;
    	}
    
    	System.out.println(time);
    	
    	
    	
    	
    	}
} Main public static void main(String[] args) throws IOException {
    
    	Scanner scan = new Scanner(System.in);
    	
    	
    	int n = scan.nextInt();
    	int x = scan.nextInt();
    	int t = scan.nextInt();
    	
    	
    	int time = 0;
    	
    	while (n > 0) {
    		n -= x;
    		time += t;
    	}
    
    	System.out.println(time);
    	
    	
    	
    	
    	} main {
    
    	Scanner scan = new Scanner(System.in);
    	
    	
    	int n = scan.nextInt();
    	int x = scan.nextInt();
    	int t = scan.nextInt();
    	
    	
    	int time = 0;
    	
    	while (n > 0) {
    		n -= x;
    		time += t;
    	}
    
    	System.out.println(time);
    	
    	
    	
    	
    	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int n = scan.nextInt(); n scan.nextInt() scan.nextInt scan int x = scan.nextInt(); x scan.nextInt() scan.nextInt scan int t = scan.nextInt(); t scan.nextInt() scan.nextInt scan int time = 0; time 0 while (n > 0) {
    		n -= x;
    		time += t;
    	} n > 0 n 0 {
    		n -= x;
    		time += t;
    	} n -= x n x time += t time t System.out.println(time) System.out.println System.out System System.out time String[] args args public class Main {


    public static void main(String[] args) throws IOException {
    
    	Scanner scan = new Scanner(System.in);
    	
    	
    	int n = scan.nextInt();
    	int x = scan.nextInt();
    	int t = scan.nextInt();
    	
    	
    	int time = 0;
    	
    	while (n > 0) {
    		n -= x;
    		time += t;
    	}
    
    	System.out.println(time);
    	
    	
    	
    	
    	}
} public class Main {


    public static void main(String[] args) throws IOException {
    
    	Scanner scan = new Scanner(System.in);
    	
    	
    	int n = scan.nextInt();
    	int x = scan.nextInt();
    	int t = scan.nextInt();
    	
    	
    	int time = 0;
    	
    	while (n > 0) {
    		n -= x;
    		time += t;
    	}
    
    	System.out.println(time);
    	
    	
    	
    	
    	}
} Main
import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.regex.*;

public class Main {


    public static void main(String[] args) throws IOException {
    
    	Scanner scan = new Scanner(System.in);
    	
    	
    	int n = scan.nextInt();
    	int x = scan.nextInt();
    	int t = scan.nextInt();
    	
    	
    	int time = 0;
    	
    	while (n > 0) {
    		n -= x;
    		time += t;
    	}
    
    	System.out.println(time);
    	
    	
    	
    	
    	}
}
