学步园

#include<iostream>
#include<stack>
using namespace std;
int main()
{
	stack<long long>s;
	long long n,t,sum;
	sum=0;
	scanf("%lld",&n);
	while(n--)
	{
		scanf("%lld",&t);
		while(s.size()>0&&s.top()<=t)
			s.pop();
		sum+=s.size();
		s.push(t);
	}
	printf("%lld\n",sum);
}

单调栈