import java.util.*;
public class Main {
    public static void main(String args[]) {
        Scanner sc = new Scanner(System.in);
        

        int n = sc.nextInt();
        int[] A = new int[n];
        for(int i =0; i < n; i++){
            A[i] = sc.nextInt();
        }
         

         int[] help = new int[n];
         help[0] = A[0];
         for(int i = 1; i < n; i++){
            if(A[i-1] >= A[i] )
               help[i] = help[i-1];

            else if(A[i] > A[i-1] && A[i] > help[i-1])
               help[i] = A[i];
             else if(A[i] > A[i-1] && A[i] < help[i-1])
               help[i] = help[i-1];
         }
         long minH = 0L;
         for(int j = 0; j < n; j++){
             minH += Math.abs(A[j] - help[j]);
         }
         System.out.println(minH);
    }
}
/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