import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.LineNumberReader;
import java.util.*;
public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n=sc.nextInt(),x=sc.nextInt(),t=sc.nextInt();
//        System.out.println((n+x-1)/x*t);
        int ans=n/x;
        if (n%x!=0){
            ans++;
        }
        System.out.println(ans*t);



    }




    static void sort(int[] a) {
        ArrayList<Integer> l=new ArrayList<>();
        for (int i:a) l.add(i);
        Collections.sort(l);
        for (int i=0; i<a.length; i++) a[i]=l.get(i);
    }
    static void sortReverse(long[] a) {
        ArrayList<Long> l=new ArrayList<>();
        for (long i:a) l.add(i);
//        Collections.sort.(l);
        Collections.sort(l,Collections.reverseOrder());
        for (int i=0; i<a.length; i++) a[i]=l.get(i);
    }

    static class FastScanner {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st=new StringTokenizer("");
        String next() {
            while (!st.hasMoreTokens())
                try {
                    st=new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }
        int[] readArray(int n) {
            int[] a=new int[n];
            for (int i=0; i<n; i++) a[i]=nextInt();
            return a;
        }
        long nextLong() {
            return Long.parseLong(next());
        }
    }


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

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n=sc.nextInt(),x=sc.nextInt(),t=sc.nextInt();
//        System.out.println((n+x-1)/x*t);
        int ans=n/x;
        if (n%x!=0){
            ans++;
        }
        System.out.println(ans*t);



    }




    static void sort(int[] a) {
        ArrayList<Integer> l=new ArrayList<>();
        for (int i:a) l.add(i);
        Collections.sort(l);
        for (int i=0; i<a.length; i++) a[i]=l.get(i);
    }
    static void sortReverse(long[] a) {
        ArrayList<Long> l=new ArrayList<>();
        for (long i:a) l.add(i);
//        Collections.sort.(l);
        Collections.sort(l,Collections.reverseOrder());
        for (int i=0; i<a.length; i++) a[i]=l.get(i);
    }

    static class FastScanner {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st=new StringTokenizer("");
        String next() {
            while (!st.hasMoreTokens())
                try {
                    st=new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }
        int[] readArray(int n) {
            int[] a=new int[n];
            for (int i=0; i<n; i++) a[i]=nextInt();
            return a;
        }
        long nextLong() {
            return Long.parseLong(next());
        }
    }


} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n=sc.nextInt(),x=sc.nextInt(),t=sc.nextInt();
//        System.out.println((n+x-1)/x*t);
        int ans=n/x;
        if (n%x!=0){
            ans++;
        }
        System.out.println(ans*t);



    } main {
        Scanner sc = new Scanner(System.in);
        int n=sc.nextInt(),x=sc.nextInt(),t=sc.nextInt();
//        System.out.println((n+x-1)/x*t);
        int ans=n/x;
        if (n%x!=0){
            ans++;
        }
        System.out.println(ans*t);



    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n=sc.nextInt() n sc.nextInt() sc.nextInt sc x=sc.nextInt() x sc.nextInt() sc.nextInt sc t=sc.nextInt(); t sc.nextInt() sc.nextInt sc int ans=n/x; ans n/x n x if (n%x!=0){
            ans++;
        } n%x!=0 n%x n x 0 {
            ans++;
        } ans++ ans System.out.println(ans*t) System.out.println System.out System System.out ans*t ans t String[] args args static void sort(int[] a) {
        ArrayList<Integer> l=new ArrayList<>();
        for (int i:a) l.add(i);
        Collections.sort(l);
        for (int i=0; i<a.length; i++) a[i]=l.get(i);
    } sort {
        ArrayList<Integer> l=new ArrayList<>();
        for (int i:a) l.add(i);
        Collections.sort(l);
        for (int i=0; i<a.length; i++) a[i]=l.get(i);
    } ArrayList<Integer> l=new ArrayList<>(); l new ArrayList<>() for (int i:a) l.add(i); int i a l.add(i); l.add(i) l.add l i Collections.sort(l) Collections.sort Collections l for (int i=0; i<a.length; i++) a[i]=l.get(i); int i=0; int i=0; i 0 i<a.length i a.length a a.length i++ i++ i a[i]=l.get(i); a[i]=l.get(i) a[i] a i l.get(i) l.get l i int[] a a static void sortReverse(long[] a) {
        ArrayList<Long> l=new ArrayList<>();
        for (long i:a) l.add(i);
//        Collections.sort.(l);
        Collections.sort(l,Collections.reverseOrder());
        for (int i=0; i<a.length; i++) a[i]=l.get(i);
    } sortReverse {
        ArrayList<Long> l=new ArrayList<>();
        for (long i:a) l.add(i);
//        Collections.sort.(l);
        Collections.sort(l,Collections.reverseOrder());
        for (int i=0; i<a.length; i++) a[i]=l.get(i);
    } ArrayList<Long> l=new ArrayList<>(); l new ArrayList<>() for (long i:a) l.add(i); long i a l.add(i); l.add(i) l.add l i Collections.sort(l,Collections.reverseOrder()) Collections.sort Collections l Collections.reverseOrder() Collections.reverseOrder Collections for (int i=0; i<a.length; i++) a[i]=l.get(i); int i=0; int i=0; i 0 i<a.length i a.length a a.length i++ i++ i a[i]=l.get(i); a[i]=l.get(i) a[i] a i l.get(i) l.get l i long[] a a static class FastScanner {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st=new StringTokenizer("");
        String next() {
            while (!st.hasMoreTokens())
                try {
                    st=new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }
        int[] readArray(int n) {
            int[] a=new int[n];
            for (int i=0; i<n; i++) a[i]=nextInt();
            return a;
        }
        long nextLong() {
            return Long.parseLong(next());
        }
    } FastScanner BufferedReader br=new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) StringTokenizer st=new StringTokenizer(""); st new StringTokenizer("") String next() {
            while (!st.hasMoreTokens())
                try {
                    st=new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            return st.nextToken();
        } next {
            while (!st.hasMoreTokens())
                try {
                    st=new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            return st.nextToken();
        } while (!st.hasMoreTokens())
                try {
                    st=new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                } !st.hasMoreTokens() st.hasMoreTokens() st.hasMoreTokens st try {
                    st=new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                } IOException e {
                    e.printStackTrace();
                } e.printStackTrace() e.printStackTrace e {
                    st=new StringTokenizer(br.readLine());
                } st=new StringTokenizer(br.readLine()) st new StringTokenizer(br.readLine()) return st.nextToken(); st.nextToken() st.nextToken st int nextInt() {
            return Integer.parseInt(next());
        } nextInt {
            return Integer.parseInt(next());
        } return Integer.parseInt(next()); Integer.parseInt(next()) Integer.parseInt Integer next() next int[] readArray(int n) {
            int[] a=new int[n];
            for (int i=0; i<n; i++) a[i]=nextInt();
            return a;
        } readArray {
            int[] a=new int[n];
            for (int i=0; i<n; i++) a[i]=nextInt();
            return a;
        } int[] a=new int[n]; a new int[n] n for (int i=0; i<n; i++) a[i]=nextInt(); int i=0; int i=0; i 0 i<n i n i++ i++ i a[i]=nextInt(); a[i]=nextInt() a[i] a i nextInt() nextInt return a; a int n n long nextLong() {
            return Long.parseLong(next());
        } nextLong {
            return Long.parseLong(next());
        } return Long.parseLong(next()); Long.parseLong(next()) Long.parseLong Long next() next public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n=sc.nextInt(),x=sc.nextInt(),t=sc.nextInt();
//        System.out.println((n+x-1)/x*t);
        int ans=n/x;
        if (n%x!=0){
            ans++;
        }
        System.out.println(ans*t);



    }




    static void sort(int[] a) {
        ArrayList<Integer> l=new ArrayList<>();
        for (int i:a) l.add(i);
        Collections.sort(l);
        for (int i=0; i<a.length; i++) a[i]=l.get(i);
    }
    static void sortReverse(long[] a) {
        ArrayList<Long> l=new ArrayList<>();
        for (long i:a) l.add(i);
//        Collections.sort.(l);
        Collections.sort(l,Collections.reverseOrder());
        for (int i=0; i<a.length; i++) a[i]=l.get(i);
    }

    static class FastScanner {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st=new StringTokenizer("");
        String next() {
            while (!st.hasMoreTokens())
                try {
                    st=new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }
        int[] readArray(int n) {
            int[] a=new int[n];
            for (int i=0; i<n; i++) a[i]=nextInt();
            return a;
        }
        long nextLong() {
            return Long.parseLong(next());
        }
    }


} public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n=sc.nextInt(),x=sc.nextInt(),t=sc.nextInt();
//        System.out.println((n+x-1)/x*t);
        int ans=n/x;
        if (n%x!=0){
            ans++;
        }
        System.out.println(ans*t);



    }




    static void sort(int[] a) {
        ArrayList<Integer> l=new ArrayList<>();
        for (int i:a) l.add(i);
        Collections.sort(l);
        for (int i=0; i<a.length; i++) a[i]=l.get(i);
    }
    static void sortReverse(long[] a) {
        ArrayList<Long> l=new ArrayList<>();
        for (long i:a) l.add(i);
//        Collections.sort.(l);
        Collections.sort(l,Collections.reverseOrder());
        for (int i=0; i<a.length; i++) a[i]=l.get(i);
    }

    static class FastScanner {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st=new StringTokenizer("");
        String next() {
            while (!st.hasMoreTokens())
                try {
                    st=new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }
        int[] readArray(int n) {
            int[] a=new int[n];
            for (int i=0; i<n; i++) a[i]=nextInt();
            return a;
        }
        long nextLong() {
            return Long.parseLong(next());
        }
    }


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

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n=sc.nextInt(),x=sc.nextInt(),t=sc.nextInt();
//        System.out.println((n+x-1)/x*t);
        int ans=n/x;
        if (n%x!=0){
            ans++;
        }
        System.out.println(ans*t);



    }




    static void sort(int[] a) {
        ArrayList<Integer> l=new ArrayList<>();
        for (int i:a) l.add(i);
        Collections.sort(l);
        for (int i=0; i<a.length; i++) a[i]=l.get(i);
    }
    static void sortReverse(long[] a) {
        ArrayList<Long> l=new ArrayList<>();
        for (long i:a) l.add(i);
//        Collections.sort.(l);
        Collections.sort(l,Collections.reverseOrder());
        for (int i=0; i<a.length; i++) a[i]=l.get(i);
    }

    static class FastScanner {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st=new StringTokenizer("");
        String next() {
            while (!st.hasMoreTokens())
                try {
                    st=new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }
        int[] readArray(int n) {
            int[] a=new int[n];
            for (int i=0; i<n; i++) a[i]=nextInt();
            return a;
        }
        long nextLong() {
            return Long.parseLong(next());
        }
    }


}