#include <bits/stdc++.h>
using namespace std;
using ll=long long;
using pll=pair<ll,ll>;
using tll=tuple<ll,ll,ll>;
using ld=long double;
const ll INF=(1ll<<60);
#define rep(i,n) for (ll i=0;i<(ll)(n);i++)
#define all(v) v.begin(),v.end()
template<class T> void chmin(T &a,T b){
    if(a>b){
        a=b;
    }
}
template<class T> void chmax(T &a,T b){
    if(a<b){
        a=b;
    }
}
int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    ll n;
    cin >> n;
    vector<ll> a(n);
    vector<vector<ll>> v(5001);
    rep(i,n){
        cin >> a[i];
        v[a[i]].push_back(i);
    }
    ll ans=0;
    rep(i,n){
        for(ll k=i+2;k<n;k++){
            if(a[i]+10!=a[k]) continue;
            for(ll j=i+1;j<k;j++){
                ll x=a[j]-a[i]-10;
                if(x<=0) continue;
                ans+=(ll)v[a[i]+x+11].size()-(upper_bound(all(v[a[i]+x+11]),k)-v[a[i]+x+11].begin());
            }
        }
    }
    cout << ans << '\n';
}