import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.charset.StandardCharsets;

public class Main {
    public static void main(String[] args) throws IOException {
        InputStreamReader reader = new InputStreamReader(System.in, StandardCharsets.UTF_8);
        BufferedReader in = new BufferedReader(reader);
        String[] str = in.readLine().split(" ");
        double n = Double.parseDouble(str[0]);
        double x = Double.parseDouble(str[1]);
        int t = Integer.parseInt(str[2]);
        System.out.println((int)Math.ceil(n/x)*t);

    }
} import java.io.BufferedReader; BufferedReader java.io import java.io.IOException; IOException java.io import java.io.InputStreamReader; InputStreamReader java.io import java.nio.charset.StandardCharsets; StandardCharsets java.nio.charset public class Main {
    public static void main(String[] args) throws IOException {
        InputStreamReader reader = new InputStreamReader(System.in, StandardCharsets.UTF_8);
        BufferedReader in = new BufferedReader(reader);
        String[] str = in.readLine().split(" ");
        double n = Double.parseDouble(str[0]);
        double x = Double.parseDouble(str[1]);
        int t = Integer.parseInt(str[2]);
        System.out.println((int)Math.ceil(n/x)*t);

    }
} Main public static void main(String[] args) throws IOException {
        InputStreamReader reader = new InputStreamReader(System.in, StandardCharsets.UTF_8);
        BufferedReader in = new BufferedReader(reader);
        String[] str = in.readLine().split(" ");
        double n = Double.parseDouble(str[0]);
        double x = Double.parseDouble(str[1]);
        int t = Integer.parseInt(str[2]);
        System.out.println((int)Math.ceil(n/x)*t);

    } main {
        InputStreamReader reader = new InputStreamReader(System.in, StandardCharsets.UTF_8);
        BufferedReader in = new BufferedReader(reader);
        String[] str = in.readLine().split(" ");
        double n = Double.parseDouble(str[0]);
        double x = Double.parseDouble(str[1]);
        int t = Integer.parseInt(str[2]);
        System.out.println((int)Math.ceil(n/x)*t);

    } InputStreamReader reader = new InputStreamReader(System.in, StandardCharsets.UTF_8); reader new InputStreamReader(System.in, StandardCharsets.UTF_8) BufferedReader in = new BufferedReader(reader); in new BufferedReader(reader) String[] str = in.readLine().split(" "); str in.readLine().split(" ") in.readLine().split in.readLine() in.readLine in " " double n = Double.parseDouble(str[0]); n Double.parseDouble(str[0]) Double.parseDouble Double str[0] str 0 double x = Double.parseDouble(str[1]); x Double.parseDouble(str[1]) Double.parseDouble Double str[1] str 1 int t = Integer.parseInt(str[2]); t Integer.parseInt(str[2]) Integer.parseInt Integer str[2] str 2 System.out.println((int)Math.ceil(n/x)*t) System.out.println System.out System System.out (int)Math.ceil(n/x)*t (int)Math.ceil(n/x) Math.ceil Math n/x n x t String[] args args public class Main {
    public static void main(String[] args) throws IOException {
        InputStreamReader reader = new InputStreamReader(System.in, StandardCharsets.UTF_8);
        BufferedReader in = new BufferedReader(reader);
        String[] str = in.readLine().split(" ");
        double n = Double.parseDouble(str[0]);
        double x = Double.parseDouble(str[1]);
        int t = Integer.parseInt(str[2]);
        System.out.println((int)Math.ceil(n/x)*t);

    }
} public class Main {
    public static void main(String[] args) throws IOException {
        InputStreamReader reader = new InputStreamReader(System.in, StandardCharsets.UTF_8);
        BufferedReader in = new BufferedReader(reader);
        String[] str = in.readLine().split(" ");
        double n = Double.parseDouble(str[0]);
        double x = Double.parseDouble(str[1]);
        int t = Integer.parseInt(str[2]);
        System.out.println((int)Math.ceil(n/x)*t);

    }
} Main
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.charset.StandardCharsets;

public class Main {
    public static void main(String[] args) throws IOException {
        InputStreamReader reader = new InputStreamReader(System.in, StandardCharsets.UTF_8);
        BufferedReader in = new BufferedReader(reader);
        String[] str = in.readLine().split(" ");
        double n = Double.parseDouble(str[0]);
        double x = Double.parseDouble(str[1]);
        int t = Integer.parseInt(str[2]);
        System.out.println((int)Math.ceil(n/x)*t);

    }
}