import java.util.*;
import java.io.*;
class Main{
	public static void main(String[]args){
		Scanner in=new Scanner(System.in);
		PrintWriter out = new PrintWriter(System.out, true);
		int n = in.nextInt();
		long max = Integer.MIN_VALUE;
		long a[]=new long[n];
		long sum = 0;
		for(int i=0;i<n;i++){
			a[i]=in.nextLong();
			max = Math.max(max, a[i]);
			sum += (a[i] < max) ? (max - a[i]) : 0;
		}
		out.println(sum);
	}
}
 import java.util.*; util.* java import java.io.*; io.* java class Main{
	public static void main(String[]args){
		Scanner in=new Scanner(System.in);
		PrintWriter out = new PrintWriter(System.out, true);
		int n = in.nextInt();
		long max = Integer.MIN_VALUE;
		long a[]=new long[n];
		long sum = 0;
		for(int i=0;i<n;i++){
			a[i]=in.nextLong();
			max = Math.max(max, a[i]);
			sum += (a[i] < max) ? (max - a[i]) : 0;
		}
		out.println(sum);
	}
} Main public static void main(String[]args){
		Scanner in=new Scanner(System.in);
		PrintWriter out = new PrintWriter(System.out, true);
		int n = in.nextInt();
		long max = Integer.MIN_VALUE;
		long a[]=new long[n];
		long sum = 0;
		for(int i=0;i<n;i++){
			a[i]=in.nextLong();
			max = Math.max(max, a[i]);
			sum += (a[i] < max) ? (max - a[i]) : 0;
		}
		out.println(sum);
	} main {
		Scanner in=new Scanner(System.in);
		PrintWriter out = new PrintWriter(System.out, true);
		int n = in.nextInt();
		long max = Integer.MIN_VALUE;
		long a[]=new long[n];
		long sum = 0;
		for(int i=0;i<n;i++){
			a[i]=in.nextLong();
			max = Math.max(max, a[i]);
			sum += (a[i] < max) ? (max - a[i]) : 0;
		}
		out.println(sum);
	} Scanner in=new Scanner(System.in); in new Scanner(System.in) PrintWriter out = new PrintWriter(System.out, true); out new PrintWriter(System.out, true) int n = in.nextInt(); n in.nextInt() in.nextInt in long max = Integer.MIN_VALUE; max Integer.MIN_VALUE Integer Integer.MIN_VALUE long a[]=new long[n]; a new long[n] n long sum = 0; sum 0 for(int i=0;i<n;i++){
			a[i]=in.nextLong();
			max = Math.max(max, a[i]);
			sum += (a[i] < max) ? (max - a[i]) : 0;
		} int i=0; int i=0; i 0 i<n i n i++ i++ i {
			a[i]=in.nextLong();
			max = Math.max(max, a[i]);
			sum += (a[i] < max) ? (max - a[i]) : 0;
		} {
			a[i]=in.nextLong();
			max = Math.max(max, a[i]);
			sum += (a[i] < max) ? (max - a[i]) : 0;
		} a[i]=in.nextLong() a[i] a i in.nextLong() in.nextLong in max = Math.max(max, a[i]) max Math.max(max, a[i]) Math.max Math max a[i] a i sum += (a[i] < max) ? (max - a[i]) : 0 sum (a[i] < max) ? (max - a[i]) : 0 (a[i] < max) a[i] a i max (max - a[i]) max a[i] a i 0 out.println(sum) out.println out sum String[]args args
import java.util.*;
import java.io.*;
class Main{
	public static void main(String[]args){
		Scanner in=new Scanner(System.in);
		PrintWriter out = new PrintWriter(System.out, true);
		int n = in.nextInt();
		long max = Integer.MIN_VALUE;
		long a[]=new long[n];
		long sum = 0;
		for(int i=0;i<n;i++){
			a[i]=in.nextLong();
			max = Math.max(max, a[i]);
			sum += (a[i] < max) ? (max - a[i]) : 0;
		}
		out.println(sum);
	}
}

