
import java.io.InputStream;
import java.io.PrintStream;
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        solve(System.in, System.out);
    }

    static void solve(InputStream is, PrintStream os) {
        // Your code here!
        Scanner scan = new Scanner(is);
        int N = scan.nextInt();
        int X = scan.nextInt();
        int T = scan.nextInt();

        int ans;

        if(N%X == 0){
            ans = N/X*T;
        } else {
            ans = (N/X+1)*T;
        }
        os.println(ans);
    }
} import java.io.InputStream; InputStream java.io import java.io.PrintStream; PrintStream java.io import java.util.*; util.* java public class Main {
    public static void main(String[] args) throws Exception {
        solve(System.in, System.out);
    }

    static void solve(InputStream is, PrintStream os) {
        // Your code here!
        Scanner scan = new Scanner(is);
        int N = scan.nextInt();
        int X = scan.nextInt();
        int T = scan.nextInt();

        int ans;

        if(N%X == 0){
            ans = N/X*T;
        } else {
            ans = (N/X+1)*T;
        }
        os.println(ans);
    }
} Main public static void main(String[] args) throws Exception {
        solve(System.in, System.out);
    } main {
        solve(System.in, System.out);
    } solve(System.in, System.out) solve System.in System System.in System.out System System.out String[] args args static void solve(InputStream is, PrintStream os) {
        // Your code here!
        Scanner scan = new Scanner(is);
        int N = scan.nextInt();
        int X = scan.nextInt();
        int T = scan.nextInt();

        int ans;

        if(N%X == 0){
            ans = N/X*T;
        } else {
            ans = (N/X+1)*T;
        }
        os.println(ans);
    } solve {
        // Your code here!
        Scanner scan = new Scanner(is);
        int N = scan.nextInt();
        int X = scan.nextInt();
        int T = scan.nextInt();

        int ans;

        if(N%X == 0){
            ans = N/X*T;
        } else {
            ans = (N/X+1)*T;
        }
        os.println(ans);
    } Scanner scan = new Scanner(is); scan new Scanner(is) 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 ans; ans if(N%X == 0){
            ans = N/X*T;
        } else {
            ans = (N/X+1)*T;
        } N%X == 0 N%X N X 0 {
            ans = N/X*T;
        } ans = N/X*T ans N/X*T N/X N X T {
            ans = (N/X+1)*T;
        } ans = (N/X+1)*T ans (N/X+1)*T (N/X+1) N/X N X 1 T os.println(ans) os.println os ans InputStream is is PrintStream os os public class Main {
    public static void main(String[] args) throws Exception {
        solve(System.in, System.out);
    }

    static void solve(InputStream is, PrintStream os) {
        // Your code here!
        Scanner scan = new Scanner(is);
        int N = scan.nextInt();
        int X = scan.nextInt();
        int T = scan.nextInt();

        int ans;

        if(N%X == 0){
            ans = N/X*T;
        } else {
            ans = (N/X+1)*T;
        }
        os.println(ans);
    }
} public class Main {
    public static void main(String[] args) throws Exception {
        solve(System.in, System.out);
    }

    static void solve(InputStream is, PrintStream os) {
        // Your code here!
        Scanner scan = new Scanner(is);
        int N = scan.nextInt();
        int X = scan.nextInt();
        int T = scan.nextInt();

        int ans;

        if(N%X == 0){
            ans = N/X*T;
        } else {
            ans = (N/X+1)*T;
        }
        os.println(ans);
    }
} Main

import java.io.InputStream;
import java.io.PrintStream;
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        solve(System.in, System.out);
    }

    static void solve(InputStream is, PrintStream os) {
        // Your code here!
        Scanner scan = new Scanner(is);
        int N = scan.nextInt();
        int X = scan.nextInt();
        int T = scan.nextInt();

        int ans;

        if(N%X == 0){
            ans = N/X*T;
        } else {
            ans = (N/X+1)*T;
        }
        os.println(ans);
    }
}