import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;

public class Main {
	 public static void main(String[] args) {
	      BufferedReader stdReader =new BufferedReader(new InputStreamReader(System.in));
	      try {
	    	  int B = Integer.parseInt(stdReader.readLine());
	    	  int N = Integer.parseInt(stdReader.readLine());
	    	  int[] num = new int[N];
	    	  long sum = B;
	    	  for(int i=0;i<N;i++){
	    		  num[i] = Integer.parseInt(stdReader.readLine());
	    		  sum += num[i];
	    	  }	    	  
	    	  Arrays.sort(num);
	    	  long center = Math.min(sum/N,num[N/2]);
	    	  long ans = 0;
	    	  for(int i=0;i<N;i++){
	    		  ans += Math.abs(num[i]-center);
	    	  }
	    	  System.out.println(ans);
	      } catch (IOException e) {
			e.printStackTrace();
	      }
	}
}