#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 4000000000000000001


int main(){
	
	int n;
	cin>>n;
	
	vector<int> a(n);
	rep(i,n)cin>>a[i];
	long long ans = 0;
	rep(i,n){
		vector<int> x(2005),y(2005);
		long long sum = 0;
		for(int j=i+1;j<n;j++){
			int t = a[j] - (a[i] + 11);
			if(t>0)y[t]++;
		}
		for(int j=i+1;j<n;j++){
			int t = a[j] - (a[i] + 11);
			if(t>0){
				y[t]--;
				sum -= x[t];
			}
			if(a[j]==a[i]+10)ans += sum;
			t = a[j] - a[i] - 10;
			if(t>0){
				x[t]++;
				sum += y[t];
			}
		}
	}
	cout<<ans<<endl;
	
	
	
	return 0;
}