import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int N = in.nextInt();
        int X = in.nextInt();
        int T = in.nextInt();
        int ans = snack(N, X, T);
        System.out.println(ans);

    }

    // 20, 12, 6
    public static int snack(int N, int X, int T) {
        int x = X;
        int t = T;
        for (; x < N; x = x + X) {
            t = t + T;
        }
        return t;
    }
} import java.util.Scanner; Scanner java.util public class Main {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int N = in.nextInt();
        int X = in.nextInt();
        int T = in.nextInt();
        int ans = snack(N, X, T);
        System.out.println(ans);

    }

    // 20, 12, 6
    public static int snack(int N, int X, int T) {
        int x = X;
        int t = T;
        for (; x < N; x = x + X) {
            t = t + T;
        }
        return t;
    }
} Main public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int N = in.nextInt();
        int X = in.nextInt();
        int T = in.nextInt();
        int ans = snack(N, X, T);
        System.out.println(ans);

    } main {
        Scanner in = new Scanner(System.in);
        int N = in.nextInt();
        int X = in.nextInt();
        int T = in.nextInt();
        int ans = snack(N, X, T);
        System.out.println(ans);

    } Scanner in = new Scanner(System.in); in new Scanner(System.in) int N = in.nextInt(); N in.nextInt() in.nextInt in int X = in.nextInt(); X in.nextInt() in.nextInt in int T = in.nextInt(); T in.nextInt() in.nextInt in int ans = snack(N, X, T); ans snack(N, X, T) snack N X T System.out.println(ans) System.out.println System.out System System.out ans String[] args args // 20, 12, 6
    public static int snack(int N, int X, int T) {
        int x = X;
        int t = T;
        for (; x < N; x = x + X) {
            t = t + T;
        }
        return t;
    } snack {
        int x = X;
        int t = T;
        for (; x < N; x = x + X) {
            t = t + T;
        }
        return t;
    } int x = X; x X int t = T; t T for (; x < N; x = x + X) {
            t = t + T;
        } ; x < N x N x = x + X x = x + X x x + X x X {
            t = t + T;
        } {
            t = t + T;
        } t = t + T t t + T t T return t; t int N N int X X int T T public class Main {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int N = in.nextInt();
        int X = in.nextInt();
        int T = in.nextInt();
        int ans = snack(N, X, T);
        System.out.println(ans);

    }

    // 20, 12, 6
    public static int snack(int N, int X, int T) {
        int x = X;
        int t = T;
        for (; x < N; x = x + X) {
            t = t + T;
        }
        return t;
    }
} public class Main {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int N = in.nextInt();
        int X = in.nextInt();
        int T = in.nextInt();
        int ans = snack(N, X, T);
        System.out.println(ans);

    }

    // 20, 12, 6
    public static int snack(int N, int X, int T) {
        int x = X;
        int t = T;
        for (; x < N; x = x + X) {
            t = t + T;
        }
        return t;
    }
} Main
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int N = in.nextInt();
        int X = in.nextInt();
        int T = in.nextInt();
        int ans = snack(N, X, T);
        System.out.println(ans);

    }

    // 20, 12, 6
    public static int snack(int N, int X, int T) {
        int x = X;
        int t = T;
        for (; x < N; x = x + X) {
            t = t + T;
        }
        return t;
    }
}
