import java.util.Arrays;
import java.util.Scanner;

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();
        long ans = 0;
        int max = Integer.MIN_VALUE;
        for (int i = 0; i < n; i++) {
            max = Math.max(max, a[i]);
            ans += max - a[i];
        }
        System.out.println(ans);
        sc.close();
    }
} import java.util.Arrays; Arrays java.util import java.util.Scanner; Scanner 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();
        long ans = 0;
        int max = Integer.MIN_VALUE;
        for (int i = 0; i < n; i++) {
            max = Math.max(max, a[i]);
            ans += max - a[i];
        }
        System.out.println(ans);
        sc.close();
    }
} 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();
        long ans = 0;
        int max = Integer.MIN_VALUE;
        for (int i = 0; i < n; i++) {
            max = Math.max(max, a[i]);
            ans += max - a[i];
        }
        System.out.println(ans);
        sc.close();
    } 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();
        long ans = 0;
        int max = Integer.MIN_VALUE;
        for (int i = 0; i < n; i++) {
            max = Math.max(max, a[i]);
            ans += max - a[i];
        }
        System.out.println(ans);
        sc.close();
    } 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] a i sc.nextInt() sc.nextInt sc long ans = 0; ans 0 int max = Integer.MIN_VALUE; max Integer.MIN_VALUE Integer Integer.MIN_VALUE for (int i = 0; i < n; i++) {
            max = Math.max(max, a[i]);
            ans += max - a[i];
        } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
            max = Math.max(max, a[i]);
            ans += max - a[i];
        } {
            max = Math.max(max, a[i]);
            ans += max - a[i];
        } max = Math.max(max, a[i]) max Math.max(max, a[i]) Math.max Math max a[i] a i ans += max - a[i] ans max - a[i] max a[i] a i System.out.println(ans) System.out.println System.out System System.out ans sc.close() sc.close sc 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();
        long ans = 0;
        int max = Integer.MIN_VALUE;
        for (int i = 0; i < n; i++) {
            max = Math.max(max, a[i]);
            ans += max - a[i];
        }
        System.out.println(ans);
        sc.close();
    }
} 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();
        long ans = 0;
        int max = Integer.MIN_VALUE;
        for (int i = 0; i < n; i++) {
            max = Math.max(max, a[i]);
            ans += max - a[i];
        }
        System.out.println(ans);
        sc.close();
    }
} Main
import java.util.Arrays;
import java.util.Scanner;

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();
        long ans = 0;
        int max = Integer.MIN_VALUE;
        for (int i = 0; i < n; i++) {
            max = Math.max(max, a[i]);
            ans += max - a[i];
        }
        System.out.println(ans);
        sc.close();
    }
}