import java.util.*;
import java.lang.*;

public class Main{
    public static void main(String[]args){
	int ans=0;
	
        Scanner sc = new Scanner(System.in);
	int N=sc.nextInt();
	int a[]=new int[N];
	int b[]=new int[N];
	a[0]=sc.nextInt();
	b[0]=a[0];
	long a_sum=a[0];
	long b_sum=b[0];
	
	for(int i=1; i<N; i++){
	    a[i]=sc.nextInt();
	    a_sum+=a[i];
	    b[i]=a[i];
	    if(b[i]<b[i-1]){
		b[i]=b[i-1];
	    }
	    b_sum+=b[i];
	}
	
	System.out.println(b_sum-a_sum);
	
    }
} import java.util.*; util.* java import java.lang.*; lang.* java public class Main{
    public static void main(String[]args){
	int ans=0;
	
        Scanner sc = new Scanner(System.in);
	int N=sc.nextInt();
	int a[]=new int[N];
	int b[]=new int[N];
	a[0]=sc.nextInt();
	b[0]=a[0];
	long a_sum=a[0];
	long b_sum=b[0];
	
	for(int i=1; i<N; i++){
	    a[i]=sc.nextInt();
	    a_sum+=a[i];
	    b[i]=a[i];
	    if(b[i]<b[i-1]){
		b[i]=b[i-1];
	    }
	    b_sum+=b[i];
	}
	
	System.out.println(b_sum-a_sum);
	
    }
} Main public static void main(String[]args){
	int ans=0;
	
        Scanner sc = new Scanner(System.in);
	int N=sc.nextInt();
	int a[]=new int[N];
	int b[]=new int[N];
	a[0]=sc.nextInt();
	b[0]=a[0];
	long a_sum=a[0];
	long b_sum=b[0];
	
	for(int i=1; i<N; i++){
	    a[i]=sc.nextInt();
	    a_sum+=a[i];
	    b[i]=a[i];
	    if(b[i]<b[i-1]){
		b[i]=b[i-1];
	    }
	    b_sum+=b[i];
	}
	
	System.out.println(b_sum-a_sum);
	
    } main {
	int ans=0;
	
        Scanner sc = new Scanner(System.in);
	int N=sc.nextInt();
	int a[]=new int[N];
	int b[]=new int[N];
	a[0]=sc.nextInt();
	b[0]=a[0];
	long a_sum=a[0];
	long b_sum=b[0];
	
	for(int i=1; i<N; i++){
	    a[i]=sc.nextInt();
	    a_sum+=a[i];
	    b[i]=a[i];
	    if(b[i]<b[i-1]){
		b[i]=b[i-1];
	    }
	    b_sum+=b[i];
	}
	
	System.out.println(b_sum-a_sum);
	
    } int ans=0; ans 0 Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N=sc.nextInt(); N sc.nextInt() sc.nextInt sc int a[]=new int[N]; a new int[N] N int b[]=new int[N]; b new int[N] N a[0]=sc.nextInt() a[0] a 0 sc.nextInt() sc.nextInt sc b[0]=a[0] b[0] b 0 a[0] a 0 long a_sum=a[0]; a_sum a[0] a 0 long b_sum=b[0]; b_sum b[0] b 0 for(int i=1; i<N; i++){
	    a[i]=sc.nextInt();
	    a_sum+=a[i];
	    b[i]=a[i];
	    if(b[i]<b[i-1]){
		b[i]=b[i-1];
	    }
	    b_sum+=b[i];
	} int i=1; int i=1; i 1 i<N i N i++ i++ i {
	    a[i]=sc.nextInt();
	    a_sum+=a[i];
	    b[i]=a[i];
	    if(b[i]<b[i-1]){
		b[i]=b[i-1];
	    }
	    b_sum+=b[i];
	} {
	    a[i]=sc.nextInt();
	    a_sum+=a[i];
	    b[i]=a[i];
	    if(b[i]<b[i-1]){
		b[i]=b[i-1];
	    }
	    b_sum+=b[i];
	} a[i]=sc.nextInt() a[i] a i sc.nextInt() sc.nextInt sc a_sum+=a[i] a_sum a[i] a i b[i]=a[i] b[i] b i a[i] a i if(b[i]<b[i-1]){
		b[i]=b[i-1];
	    } b[i]<b[i-1] b[i] b i b[i-1] b i-1 i 1 {
		b[i]=b[i-1];
	    } b[i]=b[i-1] b[i] b i b[i-1] b i-1 i 1 b_sum+=b[i] b_sum b[i] b i System.out.println(b_sum-a_sum) System.out.println System.out System System.out b_sum-a_sum b_sum a_sum String[]args args public class Main{
    public static void main(String[]args){
	int ans=0;
	
        Scanner sc = new Scanner(System.in);
	int N=sc.nextInt();
	int a[]=new int[N];
	int b[]=new int[N];
	a[0]=sc.nextInt();
	b[0]=a[0];
	long a_sum=a[0];
	long b_sum=b[0];
	
	for(int i=1; i<N; i++){
	    a[i]=sc.nextInt();
	    a_sum+=a[i];
	    b[i]=a[i];
	    if(b[i]<b[i-1]){
		b[i]=b[i-1];
	    }
	    b_sum+=b[i];
	}
	
	System.out.println(b_sum-a_sum);
	
    }
} public class Main{
    public static void main(String[]args){
	int ans=0;
	
        Scanner sc = new Scanner(System.in);
	int N=sc.nextInt();
	int a[]=new int[N];
	int b[]=new int[N];
	a[0]=sc.nextInt();
	b[0]=a[0];
	long a_sum=a[0];
	long b_sum=b[0];
	
	for(int i=1; i<N; i++){
	    a[i]=sc.nextInt();
	    a_sum+=a[i];
	    b[i]=a[i];
	    if(b[i]<b[i-1]){
		b[i]=b[i-1];
	    }
	    b_sum+=b[i];
	}
	
	System.out.println(b_sum-a_sum);
	
    }
} Main
import java.util.*;
import java.lang.*;

public class Main{
    public static void main(String[]args){
	int ans=0;
	
        Scanner sc = new Scanner(System.in);
	int N=sc.nextInt();
	int a[]=new int[N];
	int b[]=new int[N];
	a[0]=sc.nextInt();
	b[0]=a[0];
	long a_sum=a[0];
	long b_sum=b[0];
	
	for(int i=1; i<N; i++){
	    a[i]=sc.nextInt();
	    a_sum+=a[i];
	    b[i]=a[i];
	    if(b[i]<b[i-1]){
		b[i]=b[i-1];
	    }
	    b_sum+=b[i];
	}
	
	System.out.println(b_sum-a_sum);
	
    }
}
