这题用动态规划，S[i][j]表示坐标i到坐标j之间最大的矩形面积，注意坐标从1开始，一直到n-1
注意元素下标即可

#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
#include<algorithm>
#include<cstdio>
#include<stdio.h>
#include<string>
#include<cstring>
#include<cmath>
#include<vector>
#include<map>
#include<set>
#include<queue>
#include<limits>
using namespace std;
//最大的矩形
const int maxn=1010;
int S[maxn][maxn];//S[i][j]表示下标i到下标j之间的最大矩形面积
int h[maxn];//h[1]-h[n]
int main()
{
	int i, j;
	int n;
	scanf("%d",&n);
	for (int i = 1; i <= n; i++)
	{
		scanf("%d",&h[i]);
	}
	int minh;
	int maxlen;
	for (int i = 1; i <= n; i++)
	{
		minh = h[i];
		maxlen = 1;
		S[i][i + 1] = h[i];
		for (int j = i+2; j <= n+1; j++)
		{
			if (h[j-1] >= minh)
			{
				maxlen++;
				S[i][j] = minh * maxlen;
			}				
			else
			{
				minh = h[j-1];
				maxlen++;
				S[i][j] = max(S[i][j-1], minh * maxlen);
			}			
		}
	}
	int maxS = -1;
	for (int i = 1; i <= n; i++)
	{
		for (int j = i + 1; j <= n+1; j++)
		{			
			if (S[i][j] > maxS)
				maxS = S[i][j];
		}
	}
	printf("%d",maxS);
	return 0;
}