import java.io.*;
import java.util.ArrayDeque;

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(System.out));
        ArrayDeque<Integer> q = new ArrayDeque<>(10000+10);
        int m =  Integer.parseInt(reader.readLine().trim());
        String[] temp = reader.readLine().split(" ");
        int[] h = new int[m+2];
        int res = 0;
        for (int i = 0; i < m; i++) {
            h[i] = Integer.parseInt(temp[i]);
        }
        for (int i = 0; i < m; i++) {
            int last = 0;//用于存放上一个较小的高度值是多少
            while(!q.isEmpty() && h[q.peek()] <= h[i]){
                //当队列非空且队头元素小于当前元素时，计算两者之间的面积
                res += (h[q.peek()] - last) * (i - q.peek() - 1);
                //更新高度值
                last = h[q.peek()];
                q.pop();
            }
            if (!q.isEmpty()){
                res += (h[i] - last) * (i - q.peek() - 1);
            }
            q.push(i);
        }
        System.out.println(res);
    }
}