# include <fstream>
# define DIM 100003
using namespace std;
int n, v[DIM], sol;

void read ()
{
	ifstream fin ("numarare.in");
	fin>>n;
	for(int i=1;i<=n;++i)
		fin>>v[i];
}

void solve ()
{
	int s, cont, i, j;
	for(int k=1;k<n;++k)
	{
		j=k+1;
		i=k;
		s=v[i]+v[j];
		++sol;
		--i;++j;
		cont=1;
		while (i>0 && j<=n && cont)
		{
			cont=0;
			if (v[i]+v[j]==s)
				++sol, cont=1;
			--i;++j;
		}
	}
}
			
int main ()
{
	read ();
	solve ();
	ofstream fout ("numarare.out");
	fout<<sol;
	return 0;
}