import java.util.*;
public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int[] arr = new int[n];
    for(int i=0;i<n;i++){
      arr[i]=sc.nextInt();
    }
    int[] max = new int[n];
    max[0]=arr[0];
    for(int i=1;i<n;i++){
      max[i]=Math.max(max[i-1],arr[i]);
    }
    long sum =0;
    for(int i=0;i<n;i++){
      sum+=max[i]-arr[i];
    }
    System.out.println(sum);
  }
} import java.util.*; util.* java public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int[] arr = new int[n];
    for(int i=0;i<n;i++){
      arr[i]=sc.nextInt();
    }
    int[] max = new int[n];
    max[0]=arr[0];
    for(int i=1;i<n;i++){
      max[i]=Math.max(max[i-1],arr[i]);
    }
    long sum =0;
    for(int i=0;i<n;i++){
      sum+=max[i]-arr[i];
    }
    System.out.println(sum);
  }
} Main public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int[] arr = new int[n];
    for(int i=0;i<n;i++){
      arr[i]=sc.nextInt();
    }
    int[] max = new int[n];
    max[0]=arr[0];
    for(int i=1;i<n;i++){
      max[i]=Math.max(max[i-1],arr[i]);
    }
    long sum =0;
    for(int i=0;i<n;i++){
      sum+=max[i]-arr[i];
    }
    System.out.println(sum);
  } main {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int[] arr = new int[n];
    for(int i=0;i<n;i++){
      arr[i]=sc.nextInt();
    }
    int[] max = new int[n];
    max[0]=arr[0];
    for(int i=1;i<n;i++){
      max[i]=Math.max(max[i-1],arr[i]);
    }
    long sum =0;
    for(int i=0;i<n;i++){
      sum+=max[i]-arr[i];
    }
    System.out.println(sum);
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc int[] arr = new int[n]; arr new int[n] n for(int i=0;i<n;i++){
      arr[i]=sc.nextInt();
    } int i=0; int i=0; i 0 i<n i n i++ i++ i {
      arr[i]=sc.nextInt();
    } {
      arr[i]=sc.nextInt();
    } arr[i]=sc.nextInt() arr[i] arr i sc.nextInt() sc.nextInt sc int[] max = new int[n]; max new int[n] n max[0]=arr[0] max[0] max 0 arr[0] arr 0 for(int i=1;i<n;i++){
      max[i]=Math.max(max[i-1],arr[i]);
    } int i=1; int i=1; i 1 i<n i n i++ i++ i {
      max[i]=Math.max(max[i-1],arr[i]);
    } {
      max[i]=Math.max(max[i-1],arr[i]);
    } max[i]=Math.max(max[i-1],arr[i]) max[i] max i Math.max(max[i-1],arr[i]) Math.max Math max[i-1] max i-1 i 1 arr[i] arr i long sum =0; sum 0 for(int i=0;i<n;i++){
      sum+=max[i]-arr[i];
    } int i=0; int i=0; i 0 i<n i n i++ i++ i {
      sum+=max[i]-arr[i];
    } {
      sum+=max[i]-arr[i];
    } sum+=max[i]-arr[i] sum max[i]-arr[i] max[i] max i arr[i] arr i System.out.println(sum) System.out.println System.out System System.out sum String[] args args public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int[] arr = new int[n];
    for(int i=0;i<n;i++){
      arr[i]=sc.nextInt();
    }
    int[] max = new int[n];
    max[0]=arr[0];
    for(int i=1;i<n;i++){
      max[i]=Math.max(max[i-1],arr[i]);
    }
    long sum =0;
    for(int i=0;i<n;i++){
      sum+=max[i]-arr[i];
    }
    System.out.println(sum);
  }
} public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int[] arr = new int[n];
    for(int i=0;i<n;i++){
      arr[i]=sc.nextInt();
    }
    int[] max = new int[n];
    max[0]=arr[0];
    for(int i=1;i<n;i++){
      max[i]=Math.max(max[i-1],arr[i]);
    }
    long sum =0;
    for(int i=0;i<n;i++){
      sum+=max[i]-arr[i];
    }
    System.out.println(sum);
  }
} Main
import java.util.*;
public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int[] arr = new int[n];
    for(int i=0;i<n;i++){
      arr[i]=sc.nextInt();
    }
    int[] max = new int[n];
    max[0]=arr[0];
    for(int i=1;i<n;i++){
      max[i]=Math.max(max[i-1],arr[i]);
    }
    long sum =0;
    for(int i=0;i<n;i++){
      sum+=max[i]-arr[i];
    }
    System.out.println(sum);
  }
}