import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

public class Main {

	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

		StringTokenizer st = new StringTokenizer(br.readLine());
		
		int N = Integer.parseInt(st.nextToken());
		int X = Integer.parseInt(st.nextToken());
		int T = Integer.parseInt(st.nextToken());
		
		int i = 1;
		int ans = 0;
		while(true) {
			ans += T;
			if(N <= (X * i))
				break;
			i++;
		}
		
		System.out.println(ans);
	}

} import java.io.BufferedReader; BufferedReader java.io import java.io.IOException; IOException java.io import java.io.InputStreamReader; InputStreamReader java.io import java.util.StringTokenizer; StringTokenizer java.util public class Main {

	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

		StringTokenizer st = new StringTokenizer(br.readLine());
		
		int N = Integer.parseInt(st.nextToken());
		int X = Integer.parseInt(st.nextToken());
		int T = Integer.parseInt(st.nextToken());
		
		int i = 1;
		int ans = 0;
		while(true) {
			ans += T;
			if(N <= (X * i))
				break;
			i++;
		}
		
		System.out.println(ans);
	}

} Main public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

		StringTokenizer st = new StringTokenizer(br.readLine());
		
		int N = Integer.parseInt(st.nextToken());
		int X = Integer.parseInt(st.nextToken());
		int T = Integer.parseInt(st.nextToken());
		
		int i = 1;
		int ans = 0;
		while(true) {
			ans += T;
			if(N <= (X * i))
				break;
			i++;
		}
		
		System.out.println(ans);
	} main {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

		StringTokenizer st = new StringTokenizer(br.readLine());
		
		int N = Integer.parseInt(st.nextToken());
		int X = Integer.parseInt(st.nextToken());
		int T = Integer.parseInt(st.nextToken());
		
		int i = 1;
		int ans = 0;
		while(true) {
			ans += T;
			if(N <= (X * i))
				break;
			i++;
		}
		
		System.out.println(ans);
	} BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) StringTokenizer st = new StringTokenizer(br.readLine()); st new StringTokenizer(br.readLine()) int N = Integer.parseInt(st.nextToken()); N Integer.parseInt(st.nextToken()) Integer.parseInt Integer st.nextToken() st.nextToken st int X = Integer.parseInt(st.nextToken()); X Integer.parseInt(st.nextToken()) Integer.parseInt Integer st.nextToken() st.nextToken st int T = Integer.parseInt(st.nextToken()); T Integer.parseInt(st.nextToken()) Integer.parseInt Integer st.nextToken() st.nextToken st int i = 1; i 1 int ans = 0; ans 0 while(true) {
			ans += T;
			if(N <= (X * i))
				break;
			i++;
		} true {
			ans += T;
			if(N <= (X * i))
				break;
			i++;
		} ans += T ans T if(N <= (X * i))
				break; N <= (X * i) N (X * i) X i break; i++ i 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 IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

		StringTokenizer st = new StringTokenizer(br.readLine());
		
		int N = Integer.parseInt(st.nextToken());
		int X = Integer.parseInt(st.nextToken());
		int T = Integer.parseInt(st.nextToken());
		
		int i = 1;
		int ans = 0;
		while(true) {
			ans += T;
			if(N <= (X * i))
				break;
			i++;
		}
		
		System.out.println(ans);
	}

} public class Main {

	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

		StringTokenizer st = new StringTokenizer(br.readLine());
		
		int N = Integer.parseInt(st.nextToken());
		int X = Integer.parseInt(st.nextToken());
		int T = Integer.parseInt(st.nextToken());
		
		int i = 1;
		int ans = 0;
		while(true) {
			ans += T;
			if(N <= (X * i))
				break;
			i++;
		}
		
		System.out.println(ans);
	}

} Main
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

public class Main {

	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

		StringTokenizer st = new StringTokenizer(br.readLine());
		
		int N = Integer.parseInt(st.nextToken());
		int X = Integer.parseInt(st.nextToken());
		int T = Integer.parseInt(st.nextToken());
		
		int i = 1;
		int ans = 0;
		while(true) {
			ans += T;
			if(N <= (X * i))
				break;
			i++;
		}
		
		System.out.println(ans);
	}

}