import java.util.*;
import java.lang.*;

public class Main{
    public static void main(String[]args){
	int ans=0;
        Scanner sc = new Scanner(System.in);
        int N=sc.nextInt();
        int X=sc.nextInt();
	int T=sc.nextInt();
        if(N%X==0){
	    ans=T*(N/X);
	}else{
	    ans=T*(N/X+1);
	}
	System.out.println(ans);
    }
} import java.util.*; util.* java import java.lang.*; lang.* java public class Main{
    public static void main(String[]args){
	int ans=0;
        Scanner sc = new Scanner(System.in);
        int N=sc.nextInt();
        int X=sc.nextInt();
	int T=sc.nextInt();
        if(N%X==0){
	    ans=T*(N/X);
	}else{
	    ans=T*(N/X+1);
	}
	System.out.println(ans);
    }
} Main public static void main(String[]args){
	int ans=0;
        Scanner sc = new Scanner(System.in);
        int N=sc.nextInt();
        int X=sc.nextInt();
	int T=sc.nextInt();
        if(N%X==0){
	    ans=T*(N/X);
	}else{
	    ans=T*(N/X+1);
	}
	System.out.println(ans);
    } main {
	int ans=0;
        Scanner sc = new Scanner(System.in);
        int N=sc.nextInt();
        int X=sc.nextInt();
	int T=sc.nextInt();
        if(N%X==0){
	    ans=T*(N/X);
	}else{
	    ans=T*(N/X+1);
	}
	System.out.println(ans);
    } int ans=0; ans 0 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 if(N%X==0){
	    ans=T*(N/X);
	}else{
	    ans=T*(N/X+1);
	} N%X==0 N%X N X 0 {
	    ans=T*(N/X);
	} ans=T*(N/X) ans T*(N/X) T (N/X) N X {
	    ans=T*(N/X+1);
	} ans=T*(N/X+1) ans T*(N/X+1) T (N/X+1) N/X N X 1 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){
	int ans=0;
        Scanner sc = new Scanner(System.in);
        int N=sc.nextInt();
        int X=sc.nextInt();
	int T=sc.nextInt();
        if(N%X==0){
	    ans=T*(N/X);
	}else{
	    ans=T*(N/X+1);
	}
	System.out.println(ans);
    }
} public class Main{
    public static void main(String[]args){
	int ans=0;
        Scanner sc = new Scanner(System.in);
        int N=sc.nextInt();
        int X=sc.nextInt();
	int T=sc.nextInt();
        if(N%X==0){
	    ans=T*(N/X);
	}else{
	    ans=T*(N/X+1);
	}
	System.out.println(ans);
    }
} Main
import java.util.*;
import java.lang.*;

public class Main{
    public static void main(String[]args){
	int ans=0;
        Scanner sc = new Scanner(System.in);
        int N=sc.nextInt();
        int X=sc.nextInt();
	int T=sc.nextInt();
        if(N%X==0){
	    ans=T*(N/X);
	}else{
	    ans=T*(N/X+1);
	}
	System.out.println(ans);
    }
}
