import java.util.Scanner;
  public class Main {
    public static void main(String[] args) {
     
        //sec--1 (definition)
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int X = sc.nextInt();
        int T = sc.nextInt();
        int ans = 0;
        
        while(N>0) {
          ans += T;
          N=N-X;
        }

        System.out.println(ans);
    }
  } import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args) {
     
        //sec--1 (definition)
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int X = sc.nextInt();
        int T = sc.nextInt();
        int ans = 0;
        
        while(N>0) {
          ans += T;
          N=N-X;
        }

        System.out.println(ans);
    }
  } Main public static void main(String[] args) {
     
        //sec--1 (definition)
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int X = sc.nextInt();
        int T = sc.nextInt();
        int ans = 0;
        
        while(N>0) {
          ans += T;
          N=N-X;
        }

        System.out.println(ans);
    } main {
     
        //sec--1 (definition)
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int X = sc.nextInt();
        int T = sc.nextInt();
        int ans = 0;
        
        while(N>0) {
          ans += T;
          N=N-X;
        }

        System.out.println(ans);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc int X = sc.nextInt(); X sc.nextInt() sc.nextInt sc int T = sc.nextInt(); T sc.nextInt() sc.nextInt sc int ans = 0; ans 0 while(N>0) {
          ans += T;
          N=N-X;
        } N>0 N 0 {
          ans += T;
          N=N-X;
        } ans += T ans T N=N-X N N-X N X System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main {
    public static void main(String[] args) {
     
        //sec--1 (definition)
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int X = sc.nextInt();
        int T = sc.nextInt();
        int ans = 0;
        
        while(N>0) {
          ans += T;
          N=N-X;
        }

        System.out.println(ans);
    }
  } public class Main {
    public static void main(String[] args) {
     
        //sec--1 (definition)
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int X = sc.nextInt();
        int T = sc.nextInt();
        int ans = 0;
        
        while(N>0) {
          ans += T;
          N=N-X;
        }

        System.out.println(ans);
    }
  } Main
import java.util.Scanner;
  public class Main {
    public static void main(String[] args) {
     
        //sec--1 (definition)
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int X = sc.nextInt();
        int T = sc.nextInt();
        int ans = 0;
        
        while(N>0) {
          ans += T;
          N=N-X;
        }

        System.out.println(ans);
    }
  }