import java.util.Scanner;

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();

		for (int i = 1; i < n+1; i++) {
			if (i * x >= n) {
				System.out.println(t * i);
				break;
			}
		}

		sc.close();
	}

} import java.util.Scanner; Scanner 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();

		for (int i = 1; i < n+1; i++) {
			if (i * x >= n) {
				System.out.println(t * i);
				break;
			}
		}

		sc.close();
	}

} 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();

		for (int i = 1; i < n+1; i++) {
			if (i * x >= n) {
				System.out.println(t * i);
				break;
			}
		}

		sc.close();
	} main {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();

		for (int i = 1; i < n+1; i++) {
			if (i * x >= n) {
				System.out.println(t * i);
				break;
			}
		}

		sc.close();
	} 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 for (int i = 1; i < n+1; i++) {
			if (i * x >= n) {
				System.out.println(t * i);
				break;
			}
		} int i = 1; int i = 1; i 1 i < n+1 i n+1 n 1 i++ i++ i {
			if (i * x >= n) {
				System.out.println(t * i);
				break;
			}
		} {
			if (i * x >= n) {
				System.out.println(t * i);
				break;
			}
		} if (i * x >= n) {
				System.out.println(t * i);
				break;
			} i * x >= n i * x i x n {
				System.out.println(t * i);
				break;
			} System.out.println(t * i) System.out.println System.out System System.out t * i t i break; sc.close() sc.close sc 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();

		for (int i = 1; i < n+1; i++) {
			if (i * x >= n) {
				System.out.println(t * i);
				break;
			}
		}

		sc.close();
	}

} 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();

		for (int i = 1; i < n+1; i++) {
			if (i * x >= n) {
				System.out.println(t * i);
				break;
			}
		}

		sc.close();
	}

} Main
import java.util.Scanner;

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();

		for (int i = 1; i < n+1; i++) {
			if (i * x >= n) {
				System.out.println(t * i);
				break;
			}
		}

		sc.close();
	}

}