#include <bits/stdc++.h>
using namespace std;
using ll=long long;
using ld=long double;
ld pie=3.141592653589793;
ll mod=998244353;
ld inf=10000999999999900;
int main(){
    ll n;
    cin >> n;
    vector<ll>a(n);
    for (ll i = 0; i < n; i++)
    {
        cin >> a[i];
    }
    map<pair<ll,ll>,ll>memo;
    ll ans=0;
    for (ll i = n-2; i >=0; i--)
    {
        for (ll j = i-1; j >=0; j--)
        {
            ll k=a[i]-a[j]-10;
            if (k<=0)
            {
                continue;
            }
            ans+=memo[{a[i]-k,a[i]-k+k+1}];
        }
        for (ll j = i+1; j <n; j++)
        {
            memo[{a[i],a[j]}]++;
        }
    }
    cout << ans << endl;
}