import java.util.*;

public class MaxSales {

    // Recursive function to find maximum
    public static int findMax(int[] arr, int n) {
        if (n == 1) return arr[0];              // base case
        return Math.max(arr[n-1], findMax(arr, n-1)); // recursive step
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        // read n
        if (!sc.hasNextInt()) {
            System.out.println("Invalid input");
            return;
        }
        int n = sc.nextInt();

        // if n is negative or too large
        if (n < 0 || n > 1000) {
            System.out.println("Invalid input");
            return;
        }

        // if n == 0, no sales → print Invalid input (as per problem statement)
        if (n == 0) {
            System.out.println("Invalid input");
            return;
        }

        int[] sales = new int[n];

        // read sales values
        for (int i = 0; i < n; i++) {
            if (!sc.hasNextInt()) {
                System.out.println("Invalid input");
                return;
            }
            int val = sc.nextInt();
            if (val < 0) {
                System.out.println("Invalid input");
                return;
            }
            sales[i] = val;
        }

        // find and print maximum
        System.out.println(findMax(sales, n));
    }
}