import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n, x, t;
        n = sc.nextInt();
        x = sc.nextInt();
        t = sc.nextInt();
        long ans = 0, tako = 0;
        while (n > tako) {
            ans += t;
            tako += x;
        }
        System.out.println(ans);
        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, x, t;
        n = sc.nextInt();
        x = sc.nextInt();
        t = sc.nextInt();
        long ans = 0, tako = 0;
        while (n > tako) {
            ans += t;
            tako += x;
        }
        System.out.println(ans);
        sc.close();
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n, x, t;
        n = sc.nextInt();
        x = sc.nextInt();
        t = sc.nextInt();
        long ans = 0, tako = 0;
        while (n > tako) {
            ans += t;
            tako += x;
        }
        System.out.println(ans);
        sc.close();
    } main {
        Scanner sc = new Scanner(System.in);
        int n, x, t;
        n = sc.nextInt();
        x = sc.nextInt();
        t = sc.nextInt();
        long ans = 0, tako = 0;
        while (n > tako) {
            ans += t;
            tako += x;
        }
        System.out.println(ans);
        sc.close();
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n n x x t; t n = sc.nextInt() n sc.nextInt() sc.nextInt sc x = sc.nextInt() x sc.nextInt() sc.nextInt sc t = sc.nextInt() t sc.nextInt() sc.nextInt sc long ans = 0 ans 0 tako = 0; tako 0 while (n > tako) {
            ans += t;
            tako += x;
        } n > tako n tako {
            ans += t;
            tako += x;
        } ans += t ans t tako += x tako x System.out.println(ans) System.out.println System.out System System.out ans 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, x, t;
        n = sc.nextInt();
        x = sc.nextInt();
        t = sc.nextInt();
        long ans = 0, tako = 0;
        while (n > tako) {
            ans += t;
            tako += x;
        }
        System.out.println(ans);
        sc.close();
    }
} public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n, x, t;
        n = sc.nextInt();
        x = sc.nextInt();
        t = sc.nextInt();
        long ans = 0, tako = 0;
        while (n > tako) {
            ans += t;
            tako += x;
        }
        System.out.println(ans);
        sc.close();
    }
} Main
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n, x, t;
        n = sc.nextInt();
        x = sc.nextInt();
        t = sc.nextInt();
        long ans = 0, tako = 0;
        while (n > tako) {
            ans += t;
            tako += x;
        }
        System.out.println(ans);
        sc.close();
    }
}