#include<bits/stdc++.h>
using namespace std;
#define int long long
const int N=2e5+10;
int a[N];
signed main()
{
	int n;scanf("%lld",&n);
	for(int i=1;i<=n;i++)scanf("%lld",&a[i]);
	int lst=a[2]-a[1],sum=2,ans=n*2-1;
	for(int i=3;i<=n;i++)
	{
		if(a[i]-a[i-1]==lst)sum++;
		else ans+=(sum-1)*(sum-2)/2,lst=a[i]-a[i-1],sum=2;
	}
	printf("%lld\n",ans+(sum-1)*(sum-2)/2);
	return 0;
}