import java.util.Scanner;
import java.util.List;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.Arrays;
import java.util.Collections;
import java.util.*;
class Main{
  public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int N = scan.nextInt();
    int X = scan.nextInt();
    int T = scan.nextInt();
    int ans = 0;
    if(N % X == 0){
      ans = (N / X) * T;
    }
    else{
      ans = (N / X);
      ans = (ans + 1 ) * T;
    }
    System.out.println(ans);
  }
}
     
      import java.util.Scanner; Scanner java.util import java.util.List; List java.util import java.util.ArrayList; ArrayList java.util import java.util.Comparator; Comparator java.util import java.util.Arrays; Arrays java.util import java.util.Collections; Collections java.util import java.util.*; util.* java class Main{
  public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int N = scan.nextInt();
    int X = scan.nextInt();
    int T = scan.nextInt();
    int ans = 0;
    if(N % X == 0){
      ans = (N / X) * T;
    }
    else{
      ans = (N / X);
      ans = (ans + 1 ) * T;
    }
    System.out.println(ans);
  }
} Main public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int N = scan.nextInt();
    int X = scan.nextInt();
    int T = scan.nextInt();
    int ans = 0;
    if(N % X == 0){
      ans = (N / X) * T;
    }
    else{
      ans = (N / X);
      ans = (ans + 1 ) * T;
    }
    System.out.println(ans);
  } main {
    Scanner scan = new Scanner(System.in);
    int N = scan.nextInt();
    int X = scan.nextInt();
    int T = scan.nextInt();
    int ans = 0;
    if(N % X == 0){
      ans = (N / X) * T;
    }
    else{
      ans = (N / X);
      ans = (ans + 1 ) * T;
    }
    System.out.println(ans);
  } Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int N = scan.nextInt(); N scan.nextInt() scan.nextInt scan int X = scan.nextInt(); X scan.nextInt() scan.nextInt scan int T = scan.nextInt(); T scan.nextInt() scan.nextInt scan int ans = 0; ans 0 if(N % X == 0){
      ans = (N / X) * T;
    }
    else{
      ans = (N / X);
      ans = (ans + 1 ) * T;
    } N % X == 0 N % X N X 0 {
      ans = (N / X) * T;
    } ans = (N / X) * T ans (N / X) * T (N / X) N X T {
      ans = (N / X);
      ans = (ans + 1 ) * T;
    } ans = (N / X) ans (N / X) N X ans = (ans + 1 ) * T ans (ans + 1 ) * T (ans + 1 ) ans 1 T System.out.println(ans) System.out.println System.out System System.out ans String[] args args
import java.util.Scanner;
import java.util.List;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.Arrays;
import java.util.Collections;
import java.util.*;
class Main{
  public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int N = scan.nextInt();
    int X = scan.nextInt();
    int T = scan.nextInt();
    int ans = 0;
    if(N % X == 0){
      ans = (N / X) * T;
    }
    else{
      ans = (N / X);
      ans = (ans + 1 ) * T;
    }
    System.out.println(ans);
  }
}
     
     