#include<fstream>
using namespace std;
ifstream f("numarare.in");
ofstream g("numarare.out");
void citeste(int &n, int v[])
{
	int i;
	f>>n;
	for(i=1;i<=n;i++){f>>v[i];
	if(i>1)v[i-1]=v[i-1]-v[i];
	}
}
int main()
{
	int n,i,j,v[100001],L[100001],nr,p;
	citeste(n,v);
	n--; nr=n; p=1 ;
	for(i=1;i<=n;i++) 
	{
		if (i<p+L[p]) 
			L[i]=min(L[2*p-i],p+L[p]-i);
		if (i+L[i]>=p+L[p])
		{
			p=i;
			while(i-L[i]-1>=1  &&  i+L[i]+1<=n  &&  v[i-L[i]-1]==v[i+L[i]+1])
				L[i]++;
		}
	}
	for(i=1;i<=n;i++)
		nr=nr+L[i];
	g<<nr;
	return 0;
}