import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int x = sc.nextInt();
    int t = sc.nextInt();
    
    int count = 0;
    if (n >= x) {
      count = n / x;
      n = n % x;
    }
    
    if (n > 0)
      count++;
    
    System.out.println(count*t);
  }
} import java.util.*; util.* java public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int x = sc.nextInt();
    int t = sc.nextInt();
    
    int count = 0;
    if (n >= x) {
      count = n / x;
      n = n % x;
    }
    
    if (n > 0)
      count++;
    
    System.out.println(count*t);
  }
} Main public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int x = sc.nextInt();
    int t = sc.nextInt();
    
    int count = 0;
    if (n >= x) {
      count = n / x;
      n = n % x;
    }
    
    if (n > 0)
      count++;
    
    System.out.println(count*t);
  } main {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int x = sc.nextInt();
    int t = sc.nextInt();
    
    int count = 0;
    if (n >= x) {
      count = n / x;
      n = n % x;
    }
    
    if (n > 0)
      count++;
    
    System.out.println(count*t);
  } 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 count = 0; count 0 if (n >= x) {
      count = n / x;
      n = n % x;
    } n >= x n x {
      count = n / x;
      n = n % x;
    } count = n / x count n / x n x n = n % x n n % x n x if (n > 0)
      count++; n > 0 n 0 count++ count System.out.println(count*t) System.out.println System.out System System.out count*t count t String[] args args public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int x = sc.nextInt();
    int t = sc.nextInt();
    
    int count = 0;
    if (n >= x) {
      count = n / x;
      n = n % x;
    }
    
    if (n > 0)
      count++;
    
    System.out.println(count*t);
  }
} public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int x = sc.nextInt();
    int t = sc.nextInt();
    
    int count = 0;
    if (n >= x) {
      count = n / x;
      n = n % x;
    }
    
    if (n > 0)
      count++;
    
    System.out.println(count*t);
  }
} Main
import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int x = sc.nextInt();
    int t = sc.nextInt();
    
    int count = 0;
    if (n >= x) {
      count = n / x;
      n = n % x;
    }
    
    if (n > 0)
      count++;
    
    System.out.println(count*t);
  }
}