#define _USE_MATH_DEFINES
#include<iostream>
#include<vector>
#include<algorithm>
#include<cmath>
#include<string>
#include<iomanip>
#include<numeric>
#include<queue>
#include<deque>
#include<stack>
#include<set>
#include<map>
#include<random>
#include<bitset>
#include<cassert>
#include<complex>
#include<fstream>
#include<cstdlib>
#include<functional>
#include<array>
using namespace std;
typedef long long ll;
const int mod=998244353;
const int dx[]={1,0,0,-1},dy[]={0,1,-1,0};
int main(){
	static int n,a[200000];
	cin>>n;
	for(int i=0;i<n;i++)
		cin>>a[i];
	ll ans=0;
	int tmp=0;
	for(int i=1;i<n;i++){
		if(abs(a[i]-a[i-1])!=1){
			tmp=0;
			continue;
		}
		if(i>=2&&a[i]!=a[i-2])
			tmp++;
		else
			tmp=1;
		ans+=tmp;
	}
	cout<<ans<<endl;
}