import java.util.Scanner;

public class Main {
	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		long x = sc.nextLong();
		long t = sc.nextLong();
		if(n <= x) {
			System.out.println(t);
			return;
		}
		long ans = 0;
		ans += (n / x) * t;
		n %= x;
		if(n > 0) {
			ans += t;
		}

		sc.close();
		System.out.println(ans);

	}
}
 import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		long x = sc.nextLong();
		long t = sc.nextLong();
		if(n <= x) {
			System.out.println(t);
			return;
		}
		long ans = 0;
		ans += (n / x) * t;
		n %= x;
		if(n > 0) {
			ans += t;
		}

		sc.close();
		System.out.println(ans);

	}
} Main public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		long x = sc.nextLong();
		long t = sc.nextLong();
		if(n <= x) {
			System.out.println(t);
			return;
		}
		long ans = 0;
		ans += (n / x) * t;
		n %= x;
		if(n > 0) {
			ans += t;
		}

		sc.close();
		System.out.println(ans);

	} main {

		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		long x = sc.nextLong();
		long t = sc.nextLong();
		if(n <= x) {
			System.out.println(t);
			return;
		}
		long ans = 0;
		ans += (n / x) * t;
		n %= x;
		if(n > 0) {
			ans += t;
		}

		sc.close();
		System.out.println(ans);

	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) long n = sc.nextLong(); n sc.nextLong() sc.nextLong sc long x = sc.nextLong(); x sc.nextLong() sc.nextLong sc long t = sc.nextLong(); t sc.nextLong() sc.nextLong sc if(n <= x) {
			System.out.println(t);
			return;
		} n <= x n x {
			System.out.println(t);
			return;
		} System.out.println(t) System.out.println System.out System System.out t return; long ans = 0; ans 0 ans += (n / x) * t ans (n / x) * t (n / x) n x t n %= x n x if(n > 0) {
			ans += t;
		} n > 0 n 0 {
			ans += t;
		} ans += t ans t sc.close() sc.close sc 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) {

		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		long x = sc.nextLong();
		long t = sc.nextLong();
		if(n <= x) {
			System.out.println(t);
			return;
		}
		long ans = 0;
		ans += (n / x) * t;
		n %= x;
		if(n > 0) {
			ans += t;
		}

		sc.close();
		System.out.println(ans);

	}
} public class Main {
	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		long x = sc.nextLong();
		long t = sc.nextLong();
		if(n <= x) {
			System.out.println(t);
			return;
		}
		long ans = 0;
		ans += (n / x) * t;
		n %= x;
		if(n > 0) {
			ans += t;
		}

		sc.close();
		System.out.println(ans);

	}
} Main
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		long x = sc.nextLong();
		long t = sc.nextLong();
		if(n <= x) {
			System.out.println(t);
			return;
		}
		long ans = 0;
		ans += (n / x) * t;
		n %= x;
		if(n > 0) {
			ans += t;
		}

		sc.close();
		System.out.println(ans);

	}
}

