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 mx[] = new int[n];
        mx[0]=a[0];
        for(int i=1;i<n;i++){
            if(a[i]>mx[i-1]){
                mx[i]=a[i];
            }
            else{
                mx[i]=mx[i-1];
            }
        }
        long sum=0;
        for(int i=0;i<n;i++){
            if(a[i]<mx[i])
                sum+=(long)(mx[i]-a[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 a[] = new int[n];
        for(int i=0;i<n;i++){
            a[i]=sc.nextInt();
        }
        int mx[] = new int[n];
        mx[0]=a[0];
        for(int i=1;i<n;i++){
            if(a[i]>mx[i-1]){
                mx[i]=a[i];
            }
            else{
                mx[i]=mx[i-1];
            }
        }
        long sum=0;
        for(int i=0;i<n;i++){
            if(a[i]<mx[i])
                sum+=(long)(mx[i]-a[i]);
        }
        System.out.println(sum);
    }
} 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 mx[] = new int[n];
        mx[0]=a[0];
        for(int i=1;i<n;i++){
            if(a[i]>mx[i-1]){
                mx[i]=a[i];
            }
            else{
                mx[i]=mx[i-1];
            }
        }
        long sum=0;
        for(int i=0;i<n;i++){
            if(a[i]<mx[i])
                sum+=(long)(mx[i]-a[i]);
        }
        System.out.println(sum);
    } main {
        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 mx[] = new int[n];
        mx[0]=a[0];
        for(int i=1;i<n;i++){
            if(a[i]>mx[i-1]){
                mx[i]=a[i];
            }
            else{
                mx[i]=mx[i-1];
            }
        }
        long sum=0;
        for(int i=0;i<n;i++){
            if(a[i]<mx[i])
                sum+=(long)(mx[i]-a[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 a[] = new int[n]; a new int[n] n for(int i=0;i<n;i++){
            a[i]=sc.nextInt();
        } int i=0; int i=0; i 0 i<n i n i++ i++ i {
            a[i]=sc.nextInt();
        } {
            a[i]=sc.nextInt();
        } a[i]=sc.nextInt() a[i] a i sc.nextInt() sc.nextInt sc int mx[] = new int[n]; mx new int[n] n mx[0]=a[0] mx[0] mx 0 a[0] a 0 for(int i=1;i<n;i++){
            if(a[i]>mx[i-1]){
                mx[i]=a[i];
            }
            else{
                mx[i]=mx[i-1];
            }
        } int i=1; int i=1; i 1 i<n i n i++ i++ i {
            if(a[i]>mx[i-1]){
                mx[i]=a[i];
            }
            else{
                mx[i]=mx[i-1];
            }
        } {
            if(a[i]>mx[i-1]){
                mx[i]=a[i];
            }
            else{
                mx[i]=mx[i-1];
            }
        } if(a[i]>mx[i-1]){
                mx[i]=a[i];
            }
            else{
                mx[i]=mx[i-1];
            } a[i]>mx[i-1] a[i] a i mx[i-1] mx i-1 i 1 {
                mx[i]=a[i];
            } mx[i]=a[i] mx[i] mx i a[i] a i {
                mx[i]=mx[i-1];
            } mx[i]=mx[i-1] mx[i] mx i mx[i-1] mx i-1 i 1 long sum=0; sum 0 for(int i=0;i<n;i++){
            if(a[i]<mx[i])
                sum+=(long)(mx[i]-a[i]);
        } int i=0; int i=0; i 0 i<n i n i++ i++ i {
            if(a[i]<mx[i])
                sum+=(long)(mx[i]-a[i]);
        } {
            if(a[i]<mx[i])
                sum+=(long)(mx[i]-a[i]);
        } if(a[i]<mx[i])
                sum+=(long)(mx[i]-a[i]); a[i]<mx[i] a[i] a i mx[i] mx i sum+=(long)(mx[i]-a[i]) sum (long)(mx[i]-a[i]) mx[i] mx i a[i] a 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 a[] = new int[n];
        for(int i=0;i<n;i++){
            a[i]=sc.nextInt();
        }
        int mx[] = new int[n];
        mx[0]=a[0];
        for(int i=1;i<n;i++){
            if(a[i]>mx[i-1]){
                mx[i]=a[i];
            }
            else{
                mx[i]=mx[i-1];
            }
        }
        long sum=0;
        for(int i=0;i<n;i++){
            if(a[i]<mx[i])
                sum+=(long)(mx[i]-a[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 a[] = new int[n];
        for(int i=0;i<n;i++){
            a[i]=sc.nextInt();
        }
        int mx[] = new int[n];
        mx[0]=a[0];
        for(int i=1;i<n;i++){
            if(a[i]>mx[i-1]){
                mx[i]=a[i];
            }
            else{
                mx[i]=mx[i-1];
            }
        }
        long sum=0;
        for(int i=0;i<n;i++){
            if(a[i]<mx[i])
                sum+=(long)(mx[i]-a[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 a[] = new int[n];
        for(int i=0;i<n;i++){
            a[i]=sc.nextInt();
        }
        int mx[] = new int[n];
        mx[0]=a[0];
        for(int i=1;i<n;i++){
            if(a[i]>mx[i-1]){
                mx[i]=a[i];
            }
            else{
                mx[i]=mx[i-1];
            }
        }
        long sum=0;
        for(int i=0;i<n;i++){
            if(a[i]<mx[i])
                sum+=(long)(mx[i]-a[i]);
        }
        System.out.println(sum);
    }
}