import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;
import java.util.Arrays;
import java.lang.Math;

public class Main {

    public static void main(String[] args) {
        FastScanner fs = new FastScanner();
        int N = fs.nextInt(); int X = fs.nextInt(); int T = fs.nextInt();

        int times = 0;
        if (N%X != 0) {
            times+= N/X;
            times+= 1;
        } else {
            times+=N/X;
        }
        System.out.println(times*T);

    }


    static class FastScanner {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st=new StringTokenizer("");

        public String next() {
            while (!st.hasMoreElements())
                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;
        }
    }

}
 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 import java.util.Arrays; Arrays java.util import java.lang.Math; Math java.lang public class Main {

    public static void main(String[] args) {
        FastScanner fs = new FastScanner();
        int N = fs.nextInt(); int X = fs.nextInt(); int T = fs.nextInt();

        int times = 0;
        if (N%X != 0) {
            times+= N/X;
            times+= 1;
        } else {
            times+=N/X;
        }
        System.out.println(times*T);

    }


    static class FastScanner {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st=new StringTokenizer("");

        public String next() {
            while (!st.hasMoreElements())
                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;
        }
    }

} Main public static void main(String[] args) {
        FastScanner fs = new FastScanner();
        int N = fs.nextInt(); int X = fs.nextInt(); int T = fs.nextInt();

        int times = 0;
        if (N%X != 0) {
            times+= N/X;
            times+= 1;
        } else {
            times+=N/X;
        }
        System.out.println(times*T);

    } main {
        FastScanner fs = new FastScanner();
        int N = fs.nextInt(); int X = fs.nextInt(); int T = fs.nextInt();

        int times = 0;
        if (N%X != 0) {
            times+= N/X;
            times+= 1;
        } else {
            times+=N/X;
        }
        System.out.println(times*T);

    } FastScanner fs = new FastScanner(); fs new FastScanner() int N = fs.nextInt(); N fs.nextInt() fs.nextInt fs int X = fs.nextInt(); X fs.nextInt() fs.nextInt fs int T = fs.nextInt(); T fs.nextInt() fs.nextInt fs int times = 0; times 0 if (N%X != 0) {
            times+= N/X;
            times+= 1;
        } else {
            times+=N/X;
        } N%X != 0 N%X N X 0 {
            times+= N/X;
            times+= 1;
        } times+= N/X times N/X N X times+= 1 times 1 {
            times+=N/X;
        } times+=N/X times N/X N X System.out.println(times*T) System.out.println System.out System System.out times*T times T String[] args args static class FastScanner {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st=new StringTokenizer("");

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

    public static void main(String[] args) {
        FastScanner fs = new FastScanner();
        int N = fs.nextInt(); int X = fs.nextInt(); int T = fs.nextInt();

        int times = 0;
        if (N%X != 0) {
            times+= N/X;
            times+= 1;
        } else {
            times+=N/X;
        }
        System.out.println(times*T);

    }


    static class FastScanner {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st=new StringTokenizer("");

        public String next() {
            while (!st.hasMoreElements())
                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;
        }
    }

} public class Main {

    public static void main(String[] args) {
        FastScanner fs = new FastScanner();
        int N = fs.nextInt(); int X = fs.nextInt(); int T = fs.nextInt();

        int times = 0;
        if (N%X != 0) {
            times+= N/X;
            times+= 1;
        } else {
            times+=N/X;
        }
        System.out.println(times*T);

    }


    static class FastScanner {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st=new StringTokenizer("");

        public String next() {
            while (!st.hasMoreElements())
                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;
        }
    }

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

public class Main {

    public static void main(String[] args) {
        FastScanner fs = new FastScanner();
        int N = fs.nextInt(); int X = fs.nextInt(); int T = fs.nextInt();

        int times = 0;
        if (N%X != 0) {
            times+= N/X;
            times+= 1;
        } else {
            times+=N/X;
        }
        System.out.println(times*T);

    }


    static class FastScanner {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st=new StringTokenizer("");

        public String next() {
            while (!st.hasMoreElements())
                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;
        }
    }

}

