import java.util.Scanner;
class Main{
     public static void main(String args[]){
        Scanner stdin = new Scanner(System.in);
        int N = stdin.nextInt();
        int X = stdin.nextInt();
        int T = stdin.nextInt();
        int try_num = N / X;
        if (N % X != 0) try_num++;
        System.out.println(try_num * T);
    }
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz