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;
    while (true) {
      if (x * count >= n) {
        break;
      }
      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;
    while (true) {
      if (x * count >= n) {
        break;
      }
      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;
    while (true) {
      if (x * count >= n) {
        break;
      }
      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;
    while (true) {
      if (x * count >= n) {
        break;
      }
      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 while (true) {
      if (x * count >= n) {
        break;
      }
      count++;
    } true {
      if (x * count >= n) {
        break;
      }
      count++;
    } if (x * count >= n) {
        break;
      } x * count >= n x * count x count n {
        break;
      } break; 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;
    while (true) {
      if (x * count >= n) {
        break;
      }
      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;
    while (true) {
      if (x * count >= n) {
        break;
      }
      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;
    while (true) {
      if (x * count >= n) {
        break;
      }
      count++;
    }
    System.out.println(count * t);
  }
}
