#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define rep(i, n) for(int i=0;i<(n);++i)
#define rep1(i, n) for(int i=1;i<=(n);i++)
#define ll long long
using mint = modint998244353;
using P = pair<ll,ll>;
using lb = long double;
using T = tuple<ll, ll, ll>;
#ifdef LOCAL
#  include <debug_print.hpp>
#  define dbg(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#  define dbg(...) (static_cast<void>(0))
#endif

int main()
{
    int n;
    cin >> n;
    vector<int> a(n);
    rep(i,n) cin >> a[i];
    rep(i,n) --a[i];
    vector<vector<int>> cnt(2000, vector<int>(n+1));
    rep(i,n){
        cnt[a[i]][i+1]+=1;
        rep(j,2000) cnt[j][i+1] += cnt[j][i];
    }
    vector<vector<int>> idx(2000);
    rep(i,n){
        idx[a[i]].push_back(i);
    }
    ll ans = 0;
    rep(i,n){
        if(a[i]+10>=2000) continue;
        for(int id : idx[a[i]+10]) {
            for(int k=1;a[i]+k+11<2000;k++){
                int c1 = cnt[a[i]+k+10][id] - cnt[a[i]+k+10][i]; 
                int c2 = cnt[a[i]+k+11][n] - cnt[a[i]+k+11][id];
                ans += c1*c2; 
            }
        }
    }
    cout<<ans<<endl;
    return 0;
}