import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] arr = new int[n];
        for (int i = 0; i < n; i++) {
            arr[i] = sc.nextInt();
        }

        int op = 0;
        for (int i = 0; i < n; i++) {
            while (0 < arr[i]) {
                arr[i]--;
                op++;
                for (int s = i+1; s < n; s++) {
                    if (arr[s] != 0) {
                        arr[s]--;
                    } else {
                        break;
                    }
                }
            }
        }
        System.out.println(op);
    }
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz