import java.util.Scanner;

public class Main {
    static Scanner sc = new Scanner(System.in);
    static final int mod = 1000000007;

    public static void main(String[] args) {

        int  n = sc.nextInt();
         int x = sc.nextInt();
         int t = sc.nextInt();
         
         int ans = t*(n/x);
         if(n%x!=0)
         ans+= t;
         System.out.println(ans);




    }
















    static int max(int a, int b)
    {
        return Math.max(a,b);
    }
    static int max(int a, int b, int c)
    {
        return Math.max(max(a,b), c);
    }
    static int max(int a, int b, int c, int d)
    {
        return Math.max(max(a,b), max(c,d));
    }

    static int min(int a, int b)
    {
        return Math.min(a, b);
    }

    static int min(int a, int b, int c )
    {
        return Math.min(a, min(b,c));
    }

    static int min(int a, int b, int c, int d )
    {
        return Math.min(min(a,d), min(b,c));
    }

    static boolean isPower(int a, int b)
    {
        double temp = Math.log(a)/Math.log(b);
        return temp == (int) temp;
    }
    static boolean isPrime(int n)
    {
        if(n==1) return false;
        if(n==2) return true;
        if(n%2==0) return false;

        if(n<9)return true;
        if(n%3==0) return false;

        int r = (int)Math.sqrt(n);

        for(int i = 5; i<=r; i +=6)
        {
            if(n%i==0) return false;
            if(n%(i+2)==0) return false;
        }
        return true;



    }
} import java.util.Scanner; Scanner java.util public class Main {
    static Scanner sc = new Scanner(System.in);
    static final int mod = 1000000007;

    public static void main(String[] args) {

        int  n = sc.nextInt();
         int x = sc.nextInt();
         int t = sc.nextInt();
         
         int ans = t*(n/x);
         if(n%x!=0)
         ans+= t;
         System.out.println(ans);




    }
















    static int max(int a, int b)
    {
        return Math.max(a,b);
    }
    static int max(int a, int b, int c)
    {
        return Math.max(max(a,b), c);
    }
    static int max(int a, int b, int c, int d)
    {
        return Math.max(max(a,b), max(c,d));
    }

    static int min(int a, int b)
    {
        return Math.min(a, b);
    }

    static int min(int a, int b, int c )
    {
        return Math.min(a, min(b,c));
    }

    static int min(int a, int b, int c, int d )
    {
        return Math.min(min(a,d), min(b,c));
    }

    static boolean isPower(int a, int b)
    {
        double temp = Math.log(a)/Math.log(b);
        return temp == (int) temp;
    }
    static boolean isPrime(int n)
    {
        if(n==1) return false;
        if(n==2) return true;
        if(n%2==0) return false;

        if(n<9)return true;
        if(n%3==0) return false;

        int r = (int)Math.sqrt(n);

        for(int i = 5; i<=r; i +=6)
        {
            if(n%i==0) return false;
            if(n%(i+2)==0) return false;
        }
        return true;



    }
} Main static Scanner sc = new Scanner(System.in); sc new Scanner(System.in) static final int mod = 1000000007; mod 1000000007 public static void main(String[] args) {

        int  n = sc.nextInt();
         int x = sc.nextInt();
         int t = sc.nextInt();
         
         int ans = t*(n/x);
         if(n%x!=0)
         ans+= t;
         System.out.println(ans);




    } main {

        int  n = sc.nextInt();
         int x = sc.nextInt();
         int t = sc.nextInt();
         
         int ans = t*(n/x);
         if(n%x!=0)
         ans+= t;
         System.out.println(ans);




    } 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 ans = t*(n/x); ans t*(n/x) t (n/x) n x if(n%x!=0)
         ans+= t; n%x!=0 n%x n x 0 ans+= t ans t System.out.println(ans) System.out.println System.out System System.out ans String[] args args static int max(int a, int b)
    {
        return Math.max(a,b);
    } max {
        return Math.max(a,b);
    } return Math.max(a,b); Math.max(a,b) Math.max Math a b int a a int b b static int max(int a, int b, int c)
    {
        return Math.max(max(a,b), c);
    } max {
        return Math.max(max(a,b), c);
    } return Math.max(max(a,b), c); Math.max(max(a,b), c) Math.max Math max(a,b) max a b c int a a int b b int c c static int max(int a, int b, int c, int d)
    {
        return Math.max(max(a,b), max(c,d));
    } max {
        return Math.max(max(a,b), max(c,d));
    } return Math.max(max(a,b), max(c,d)); Math.max(max(a,b), max(c,d)) Math.max Math max(a,b) max a b max(c,d) max c d int a a int b b int c c int d d static int min(int a, int b)
    {
        return Math.min(a, b);
    } min {
        return Math.min(a, b);
    } return Math.min(a, b); Math.min(a, b) Math.min Math a b int a a int b b static int min(int a, int b, int c )
    {
        return Math.min(a, min(b,c));
    } min {
        return Math.min(a, min(b,c));
    } return Math.min(a, min(b,c)); Math.min(a, min(b,c)) Math.min Math a min(b,c) min b c int a a int b b int c c static int min(int a, int b, int c, int d )
    {
        return Math.min(min(a,d), min(b,c));
    } min {
        return Math.min(min(a,d), min(b,c));
    } return Math.min(min(a,d), min(b,c)); Math.min(min(a,d), min(b,c)) Math.min Math min(a,d) min a d min(b,c) min b c int a a int b b int c c int d d static boolean isPower(int a, int b)
    {
        double temp = Math.log(a)/Math.log(b);
        return temp == (int) temp;
    } isPower {
        double temp = Math.log(a)/Math.log(b);
        return temp == (int) temp;
    } double temp = Math.log(a)/Math.log(b); temp Math.log(a)/Math.log(b) Math.log(a) Math.log Math a Math.log(b) Math.log Math b return temp == (int) temp; temp == (int) temp temp (int) temp int a a int b b static boolean isPrime(int n)
    {
        if(n==1) return false;
        if(n==2) return true;
        if(n%2==0) return false;

        if(n<9)return true;
        if(n%3==0) return false;

        int r = (int)Math.sqrt(n);

        for(int i = 5; i<=r; i +=6)
        {
            if(n%i==0) return false;
            if(n%(i+2)==0) return false;
        }
        return true;



    } isPrime {
        if(n==1) return false;
        if(n==2) return true;
        if(n%2==0) return false;

        if(n<9)return true;
        if(n%3==0) return false;

        int r = (int)Math.sqrt(n);

        for(int i = 5; i<=r; i +=6)
        {
            if(n%i==0) return false;
            if(n%(i+2)==0) return false;
        }
        return true;



    } if(n==1) return false; n==1 n 1 return false; false if(n==2) return true; n==2 n 2 return true; true if(n%2==0) return false; n%2==0 n%2 n 2 0 return false; false if(n<9)return true; n<9 n 9 return true; true if(n%3==0) return false; n%3==0 n%3 n 3 0 return false; false int r = (int)Math.sqrt(n); r (int)Math.sqrt(n) Math.sqrt Math n for(int i = 5; i<=r; i +=6)
        {
            if(n%i==0) return false;
            if(n%(i+2)==0) return false;
        } int i = 5; int i = 5; i 5 i<=r i r i +=6 i +=6 i 6 {
            if(n%i==0) return false;
            if(n%(i+2)==0) return false;
        } {
            if(n%i==0) return false;
            if(n%(i+2)==0) return false;
        } if(n%i==0) return false; n%i==0 n%i n i 0 return false; false if(n%(i+2)==0) return false; n%(i+2)==0 n%(i+2) n (i+2) i 2 0 return false; false return true; true int n n public class Main {
    static Scanner sc = new Scanner(System.in);
    static final int mod = 1000000007;

    public static void main(String[] args) {

        int  n = sc.nextInt();
         int x = sc.nextInt();
         int t = sc.nextInt();
         
         int ans = t*(n/x);
         if(n%x!=0)
         ans+= t;
         System.out.println(ans);




    }
















    static int max(int a, int b)
    {
        return Math.max(a,b);
    }
    static int max(int a, int b, int c)
    {
        return Math.max(max(a,b), c);
    }
    static int max(int a, int b, int c, int d)
    {
        return Math.max(max(a,b), max(c,d));
    }

    static int min(int a, int b)
    {
        return Math.min(a, b);
    }

    static int min(int a, int b, int c )
    {
        return Math.min(a, min(b,c));
    }

    static int min(int a, int b, int c, int d )
    {
        return Math.min(min(a,d), min(b,c));
    }

    static boolean isPower(int a, int b)
    {
        double temp = Math.log(a)/Math.log(b);
        return temp == (int) temp;
    }
    static boolean isPrime(int n)
    {
        if(n==1) return false;
        if(n==2) return true;
        if(n%2==0) return false;

        if(n<9)return true;
        if(n%3==0) return false;

        int r = (int)Math.sqrt(n);

        for(int i = 5; i<=r; i +=6)
        {
            if(n%i==0) return false;
            if(n%(i+2)==0) return false;
        }
        return true;



    }
} public class Main {
    static Scanner sc = new Scanner(System.in);
    static final int mod = 1000000007;

    public static void main(String[] args) {

        int  n = sc.nextInt();
         int x = sc.nextInt();
         int t = sc.nextInt();
         
         int ans = t*(n/x);
         if(n%x!=0)
         ans+= t;
         System.out.println(ans);




    }
















    static int max(int a, int b)
    {
        return Math.max(a,b);
    }
    static int max(int a, int b, int c)
    {
        return Math.max(max(a,b), c);
    }
    static int max(int a, int b, int c, int d)
    {
        return Math.max(max(a,b), max(c,d));
    }

    static int min(int a, int b)
    {
        return Math.min(a, b);
    }

    static int min(int a, int b, int c )
    {
        return Math.min(a, min(b,c));
    }

    static int min(int a, int b, int c, int d )
    {
        return Math.min(min(a,d), min(b,c));
    }

    static boolean isPower(int a, int b)
    {
        double temp = Math.log(a)/Math.log(b);
        return temp == (int) temp;
    }
    static boolean isPrime(int n)
    {
        if(n==1) return false;
        if(n==2) return true;
        if(n%2==0) return false;

        if(n<9)return true;
        if(n%3==0) return false;

        int r = (int)Math.sqrt(n);

        for(int i = 5; i<=r; i +=6)
        {
            if(n%i==0) return false;
            if(n%(i+2)==0) return false;
        }
        return true;



    }
} Main
import java.util.Scanner;

public class Main {
    static Scanner sc = new Scanner(System.in);
    static final int mod = 1000000007;

    public static void main(String[] args) {

        int  n = sc.nextInt();
         int x = sc.nextInt();
         int t = sc.nextInt();
         
         int ans = t*(n/x);
         if(n%x!=0)
         ans+= t;
         System.out.println(ans);




    }
















    static int max(int a, int b)
    {
        return Math.max(a,b);
    }
    static int max(int a, int b, int c)
    {
        return Math.max(max(a,b), c);
    }
    static int max(int a, int b, int c, int d)
    {
        return Math.max(max(a,b), max(c,d));
    }

    static int min(int a, int b)
    {
        return Math.min(a, b);
    }

    static int min(int a, int b, int c )
    {
        return Math.min(a, min(b,c));
    }

    static int min(int a, int b, int c, int d )
    {
        return Math.min(min(a,d), min(b,c));
    }

    static boolean isPower(int a, int b)
    {
        double temp = Math.log(a)/Math.log(b);
        return temp == (int) temp;
    }
    static boolean isPrime(int n)
    {
        if(n==1) return false;
        if(n==2) return true;
        if(n%2==0) return false;

        if(n<9)return true;
        if(n%3==0) return false;

        int r = (int)Math.sqrt(n);

        for(int i = 5; i<=r; i +=6)
        {
            if(n%i==0) return false;
            if(n%(i+2)==0) return false;
        }
        return true;



    }
}
