import java.util.*;
import java.io.*;

public class Main {
    public static void main(String[] args) {
        MyScanner scn = new MyScanner();
        out = new PrintWriter(new BufferedOutputStream(System.out));

        // Start writing your solution here. -------------------------------------

        /*
         * int n = sc.nextInt(); // read input as integer long k = sc.nextLong(); //
         * read input as long double d = sc.nextDouble(); // read input as double String
         * str = sc.next(); // read input as String String s = sc.nextLine(); // read
         * whole line as String
         * 
         * int result = 3*n; out.println(result); // print via PrintWriter
         */

        // Stop writing your solution here. -------------------------------------

        long x = scn.nextLong();
        long b = scn.nextLong();
        long t = scn.nextLong();

        out.println(((x + b - 1) / b) * t);
        out.close();
    }

    public static PrintWriter out;

    public static class MyScanner {
        BufferedReader br;
        StringTokenizer st;

        public MyScanner() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }

    }

} import java.util.*; util.* java import java.io.*; io.* java public class Main {
    public static void main(String[] args) {
        MyScanner scn = new MyScanner();
        out = new PrintWriter(new BufferedOutputStream(System.out));

        // Start writing your solution here. -------------------------------------

        /*
         * int n = sc.nextInt(); // read input as integer long k = sc.nextLong(); //
         * read input as long double d = sc.nextDouble(); // read input as double String
         * str = sc.next(); // read input as String String s = sc.nextLine(); // read
         * whole line as String
         * 
         * int result = 3*n; out.println(result); // print via PrintWriter
         */

        // Stop writing your solution here. -------------------------------------

        long x = scn.nextLong();
        long b = scn.nextLong();
        long t = scn.nextLong();

        out.println(((x + b - 1) / b) * t);
        out.close();
    }

    public static PrintWriter out;

    public static class MyScanner {
        BufferedReader br;
        StringTokenizer st;

        public MyScanner() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }

    }

} Main public static PrintWriter out; out public static void main(String[] args) {
        MyScanner scn = new MyScanner();
        out = new PrintWriter(new BufferedOutputStream(System.out));

        // Start writing your solution here. -------------------------------------

        /*
         * int n = sc.nextInt(); // read input as integer long k = sc.nextLong(); //
         * read input as long double d = sc.nextDouble(); // read input as double String
         * str = sc.next(); // read input as String String s = sc.nextLine(); // read
         * whole line as String
         * 
         * int result = 3*n; out.println(result); // print via PrintWriter
         */

        // Stop writing your solution here. -------------------------------------

        long x = scn.nextLong();
        long b = scn.nextLong();
        long t = scn.nextLong();

        out.println(((x + b - 1) / b) * t);
        out.close();
    } main {
        MyScanner scn = new MyScanner();
        out = new PrintWriter(new BufferedOutputStream(System.out));

        // Start writing your solution here. -------------------------------------

        /*
         * int n = sc.nextInt(); // read input as integer long k = sc.nextLong(); //
         * read input as long double d = sc.nextDouble(); // read input as double String
         * str = sc.next(); // read input as String String s = sc.nextLine(); // read
         * whole line as String
         * 
         * int result = 3*n; out.println(result); // print via PrintWriter
         */

        // Stop writing your solution here. -------------------------------------

        long x = scn.nextLong();
        long b = scn.nextLong();
        long t = scn.nextLong();

        out.println(((x + b - 1) / b) * t);
        out.close();
    } MyScanner scn = new MyScanner(); scn new MyScanner() out = new PrintWriter(new BufferedOutputStream(System.out)) out new PrintWriter(new BufferedOutputStream(System.out)) long x = scn.nextLong(); x scn.nextLong() scn.nextLong scn long b = scn.nextLong(); b scn.nextLong() scn.nextLong scn long t = scn.nextLong(); t scn.nextLong() scn.nextLong scn out.println(((x + b - 1) / b) * t) out.println out ((x + b - 1) / b) * t ((x + b - 1) / b) (x + b - 1) x + b x b 1 b t out.close() out.close out String[] args args public static class MyScanner {
        BufferedReader br;
        StringTokenizer st;

        public MyScanner() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }

    } MyScanner BufferedReader br; br StringTokenizer st; st public MyScanner() {
            br = new BufferedReader(new InputStreamReader(System.in));
        } MyScanner {
            br = new BufferedReader(new InputStreamReader(System.in));
        } br = new BufferedReader(new InputStreamReader(System.in)) br new BufferedReader(new InputStreamReader(System.in)) String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        } next {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        } while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            } st == null || !st.hasMoreElements() st == null st null !st.hasMoreElements() st.hasMoreElements() st.hasMoreElements st {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            } 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 long nextLong() {
            return Long.parseLong(next());
        } nextLong {
            return Long.parseLong(next());
        } return Long.parseLong(next()); Long.parseLong(next()) Long.parseLong Long next() next double nextDouble() {
            return Double.parseDouble(next());
        } nextDouble {
            return Double.parseDouble(next());
        } return Double.parseDouble(next()); Double.parseDouble(next()) Double.parseDouble Double next() next String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        } nextLine {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        } String str = ""; str "" try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } IOException e {
                e.printStackTrace();
            } e.printStackTrace() e.printStackTrace e {
                str = br.readLine();
            } str = br.readLine() str br.readLine() br.readLine br return str; str public class Main {
    public static void main(String[] args) {
        MyScanner scn = new MyScanner();
        out = new PrintWriter(new BufferedOutputStream(System.out));

        // Start writing your solution here. -------------------------------------

        /*
         * int n = sc.nextInt(); // read input as integer long k = sc.nextLong(); //
         * read input as long double d = sc.nextDouble(); // read input as double String
         * str = sc.next(); // read input as String String s = sc.nextLine(); // read
         * whole line as String
         * 
         * int result = 3*n; out.println(result); // print via PrintWriter
         */

        // Stop writing your solution here. -------------------------------------

        long x = scn.nextLong();
        long b = scn.nextLong();
        long t = scn.nextLong();

        out.println(((x + b - 1) / b) * t);
        out.close();
    }

    public static PrintWriter out;

    public static class MyScanner {
        BufferedReader br;
        StringTokenizer st;

        public MyScanner() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }

    }

} public class Main {
    public static void main(String[] args) {
        MyScanner scn = new MyScanner();
        out = new PrintWriter(new BufferedOutputStream(System.out));

        // Start writing your solution here. -------------------------------------

        /*
         * int n = sc.nextInt(); // read input as integer long k = sc.nextLong(); //
         * read input as long double d = sc.nextDouble(); // read input as double String
         * str = sc.next(); // read input as String String s = sc.nextLine(); // read
         * whole line as String
         * 
         * int result = 3*n; out.println(result); // print via PrintWriter
         */

        // Stop writing your solution here. -------------------------------------

        long x = scn.nextLong();
        long b = scn.nextLong();
        long t = scn.nextLong();

        out.println(((x + b - 1) / b) * t);
        out.close();
    }

    public static PrintWriter out;

    public static class MyScanner {
        BufferedReader br;
        StringTokenizer st;

        public MyScanner() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }

    }

} Main
import java.util.*;
import java.io.*;

public class Main {
    public static void main(String[] args) {
        MyScanner scn = new MyScanner();
        out = new PrintWriter(new BufferedOutputStream(System.out));

        // Start writing your solution here. -------------------------------------

        /*
         * int n = sc.nextInt(); // read input as integer long k = sc.nextLong(); //
         * read input as long double d = sc.nextDouble(); // read input as double String
         * str = sc.next(); // read input as String String s = sc.nextLine(); // read
         * whole line as String
         * 
         * int result = 3*n; out.println(result); // print via PrintWriter
         */

        // Stop writing your solution here. -------------------------------------

        long x = scn.nextLong();
        long b = scn.nextLong();
        long t = scn.nextLong();

        out.println(((x + b - 1) / b) * t);
        out.close();
    }

    public static PrintWriter out;

    public static class MyScanner {
        BufferedReader br;
        StringTokenizer st;

        public MyScanner() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }

    }

}