using System;
using System.Text;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
using static System.Console;
using static System.Math;
namespace atcoder151
{
    public class MainClass
    {
        public static void Main(string[] args)
        {
            new MainClass().Solve(new ConsoleInput(Console.In, ' '));
        }

        public void Solve(ConsoleInput cin)
        {
            string[] array = Console.ReadLine().Split(' ').ToArray();
            int n = int.Parse(array[0]);
            int x = int.Parse(array[1]);
            int t = int.Parse(array[2]);

            //int[] h = cin.ReadIntArray(n);

            //List<int> hl = h.ToList();
            //hl.Sort();
            int ans = 0;
            if (n % x > 0 && x != 1) {
                ans = n / x + 1;
                WriteLine(ans * t);
            }
            else if (n%x == 0) {
                ans = n / x;
                WriteLine(ans * t);
            }
            else if (n < x || n == x)
            {
                ans = t;
                WriteLine(ans);
            }
            
        }


        public class ConsoleInput
        {
            //string[] arr;
            //int x;
            //int y;
            //        for (int i = 0; i<n; i++)
            //        {
            //            arr = Console.ReadLine().Split(' ').ToArray();
            //x = int.Parse(arr[0]);
            //y = int.Parse(arr[1]);
            //var power = Math.Sqrt(Math.Pow(x, 2) + Math.Pow(y, 2));
            //            if (power <= d)
            //            {
            //                counter++;
            //            }
            //        }
            private readonly System.IO.TextReader _stream;
            private char _separator = ' ';
            private Queue<string> inputStream;
            public ConsoleInput(System.IO.TextReader stream, char separator = ' ')
            {
                this._separator = separator;
                this._stream = stream;
                inputStream = new Queue<string>();
            }
            public string Read
            {
                get
                {
                    if (inputStream.Count != 0) return inputStream.Dequeue();
                    string[] tmp = _stream.ReadLine().Split(_separator);
                    for (int i = 0; i < tmp.Length; ++i)
                        inputStream.Enqueue(tmp[i]);
                    return inputStream.Dequeue();
                }
            }
            public string ReadLine { get { return _stream.ReadLine(); } }
            public int ReadInt { get { return int.Parse(Read); } }
            public long ReadLong { get { return long.Parse(Read); } }
            public double ReadDouble { get { return double.Parse(Read); } }
            public string[] ReadStrArray(long N) { var ret = new string[N]; for (long i = 0; i < N; ++i) ret[i] = Read; return ret; }
            public int[] ReadIntArray(long N) { var ret = new int[N]; for (long i = 0; i < N; ++i) ret[i] = ReadInt; return ret; }
            public long[] ReadLongArray(long N) { var ret = new long[N]; for (long i = 0; i < N; ++i) ret[i] = ReadLong; return ret; }

        }
    }
}


Measured memory_bytes: 28296