//package abc176;

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Main {
	public static void main(String[] args) throws Exception{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] ip = br.readLine().split(" ");
		
		int N = Integer.parseInt(ip[0]);
		int X = Integer.parseInt(ip[1]);
		int T = Integer.parseInt(ip[2]);
		
		int ans = N/X*T;
		
		if(N%X != 0) ans += T;
		
		System.out.println(ans);
	}
	
} import java.io.BufferedReader; BufferedReader java.io import java.io.InputStreamReader; InputStreamReader java.io public class Main {
	public static void main(String[] args) throws Exception{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] ip = br.readLine().split(" ");
		
		int N = Integer.parseInt(ip[0]);
		int X = Integer.parseInt(ip[1]);
		int T = Integer.parseInt(ip[2]);
		
		int ans = N/X*T;
		
		if(N%X != 0) ans += T;
		
		System.out.println(ans);
	}
	
} Main public static void main(String[] args) throws Exception{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] ip = br.readLine().split(" ");
		
		int N = Integer.parseInt(ip[0]);
		int X = Integer.parseInt(ip[1]);
		int T = Integer.parseInt(ip[2]);
		
		int ans = N/X*T;
		
		if(N%X != 0) ans += T;
		
		System.out.println(ans);
	} main {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] ip = br.readLine().split(" ");
		
		int N = Integer.parseInt(ip[0]);
		int X = Integer.parseInt(ip[1]);
		int T = Integer.parseInt(ip[2]);
		
		int ans = N/X*T;
		
		if(N%X != 0) ans += T;
		
		System.out.println(ans);
	} BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) String[] ip = br.readLine().split(" "); ip br.readLine().split(" ") br.readLine().split br.readLine() br.readLine br " " int N = Integer.parseInt(ip[0]); N Integer.parseInt(ip[0]) Integer.parseInt Integer ip[0] ip 0 int X = Integer.parseInt(ip[1]); X Integer.parseInt(ip[1]) Integer.parseInt Integer ip[1] ip 1 int T = Integer.parseInt(ip[2]); T Integer.parseInt(ip[2]) Integer.parseInt Integer ip[2] ip 2 int ans = N/X*T; ans N/X*T N/X N X T if(N%X != 0) ans += T; N%X != 0 N%X N X 0 ans += T ans T System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main {
	public static void main(String[] args) throws Exception{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] ip = br.readLine().split(" ");
		
		int N = Integer.parseInt(ip[0]);
		int X = Integer.parseInt(ip[1]);
		int T = Integer.parseInt(ip[2]);
		
		int ans = N/X*T;
		
		if(N%X != 0) ans += T;
		
		System.out.println(ans);
	}
	
} public class Main {
	public static void main(String[] args) throws Exception{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] ip = br.readLine().split(" ");
		
		int N = Integer.parseInt(ip[0]);
		int X = Integer.parseInt(ip[1]);
		int T = Integer.parseInt(ip[2]);
		
		int ans = N/X*T;
		
		if(N%X != 0) ans += T;
		
		System.out.println(ans);
	}
	
} Main
//package abc176;

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Main {
	public static void main(String[] args) throws Exception{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] ip = br.readLine().split(" ");
		
		int N = Integer.parseInt(ip[0]);
		int X = Integer.parseInt(ip[1]);
		int T = Integer.parseInt(ip[2]);
		
		int ans = N/X*T;
		
		if(N%X != 0) ans += T;
		
		System.out.println(ans);
	}
	
}
