import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        try (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 sum = 0;
            for (int i = 1; i < N; i++) {
                int diff = A[i] - A[i - 1];
                sum += diff < 0 ? -diff : 0;
                A[i] = Math.max(A[i] + (diff < 0 ? -diff : 0), A[i - 1]);
            }
            System.out.println(sum);
        }
    }
} import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args) {
        try (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 sum = 0;
            for (int i = 1; i < N; i++) {
                int diff = A[i] - A[i - 1];
                sum += diff < 0 ? -diff : 0;
                A[i] = Math.max(A[i] + (diff < 0 ? -diff : 0), A[i - 1]);
            }
            System.out.println(sum);
        }
    }
} Main public static void main(String[] args) {
        try (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 sum = 0;
            for (int i = 1; i < N; i++) {
                int diff = A[i] - A[i - 1];
                sum += diff < 0 ? -diff : 0;
                A[i] = Math.max(A[i] + (diff < 0 ? -diff : 0), A[i - 1]);
            }
            System.out.println(sum);
        }
    } main {
        try (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 sum = 0;
            for (int i = 1; i < N; i++) {
                int diff = A[i] - A[i - 1];
                sum += diff < 0 ? -diff : 0;
                A[i] = Math.max(A[i] + (diff < 0 ? -diff : 0), A[i - 1]);
            }
            System.out.println(sum);
        }
    } try (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 sum = 0;
            for (int i = 1; i < N; i++) {
                int diff = A[i] - A[i - 1];
                sum += diff < 0 ? -diff : 0;
                A[i] = Math.max(A[i] + (diff < 0 ? -diff : 0), A[i - 1]);
            }
            System.out.println(sum);
        } {
            int N = sc.nextInt();
            int[] A = new int[N];
            for (int i = 0; i < N; i++) {
                A[i] = sc.nextInt();
            }

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

public class Main {
    public static void main(String[] args) {
        try (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 sum = 0;
            for (int i = 1; i < N; i++) {
                int diff = A[i] - A[i - 1];
                sum += diff < 0 ? -diff : 0;
                A[i] = Math.max(A[i] + (diff < 0 ? -diff : 0), A[i - 1]);
            }
            System.out.println(sum);
        }
    }
}
