#include <bits/stdc++.h>

using namespace std;

ifstream fin("medie.in");
ofstream fout("medie.out");

int n, v[9005], fr[7005], fr2[7005], fr3[7005];
long long ans;


int main()
{
    fin >> n;
    for (int i = 1; i <= n; ++i)
        fin >> v[i];
    for (int i = 1; i < n; ++i)
    {
        for (int j = i + 1; j <= n; ++j)
        {
            if (j - i > 1) fr2[v[j - 1]]++;
            if (v[i] % 2 != v[j] % 2) continue;
            int x = (v[i] + v[j]) / 2;
            ans += fr[x] + fr2[x];
        }
        for (int j = 1; j <= 7000; ++j) fr2[j] = 0;
        fr[v[i]]++;
    }
    for (int i = n; i > 1; --i)
    {
        for (int j = i - 1; j >= 1; --j)
        {
            if (v[i] % 2 != v[j] % 2) continue;
            int x = (v[i] + v[j]) / 2;
            ans += fr3[x];
        }
        fr3[v[i]]++;
    }
    fout << ans;
    fin.close();
    fout.close();
    return 0;
}