#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];
    ll ans = 0;
    for(int k=1;k<2000;k++){
        vector<vector<ll>> dp(2001, vector<ll>(4));
        rep(i,n){
            if(a[i]-k-10>=0) {
                dp[a[i]-k-10][1] += dp[a[i]-k-10][0];
            }
            if(a[i]-10>=0) {
                dp[a[i]-10][2] += dp[a[i]-10][1];
            }
            if(a[i]-k-11>=0){
                dp[a[i]-k-11][3] += dp[a[i]-k-11][2];
            }
            dp[a[i]][0] += 1;
        }
        rep(j,2000)ans+=dp[j][3];
    }
    cout<<ans<<endl;
    return 0;
}