#include <bits/stdc++.h>

// #include <atcoder/all>

#pragma GCC target("avx")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

using namespace std;
// using namespace atcoder;

using ll = long long;
using str = string;
using pl = pair<ll, ll>;
template <typename T>
using ml = map<ll, T>;
using mll = ml<ll>;
using sl = set<ll>;
using dbl = double;
using pd = pair<dbl, dbl>;
template <typename T>
using vec = vector<T>;
template <typename T>
using vv = vec<vec<T>>;
template <typename T1, typename T2>
using vp = vec<pair<T1, T2>>;
using vl = vec<ll>;
using vvl = vec<vl>;
using vs = vec<str>;
using vc = vec<char>;
using vpl = vec<pl>;
using vd = vec<dbl>;
using vpd = vec<pd>;
using tl3 = tuple<ll, ll, ll>;

const double INF = std::numeric_limits<double>::infinity();

#define LL(x) \
    ll x;     \
    cin >> x;
#define STR(s) \
    str s;     \
    cin >> s;
#define VL(a, n) \
    vl a(n);     \
    cin >> a;

#define all(obj) (obj).begin(), (obj).end()

#define reps(i, a, n) for (ll i = (a); i < (ll)(n); ++i)
#define rep(i, n) reps(i, 0, n)
#define rrep(i, n) reps(i, 1, n + 1)
#define repds(i, a, n) for (ll i = (n - 1); i >= (a); i--)
#define repd(i, n) repds(i, 0, n)
#define rrepd(i, n) repds(i, 1, n + 1)
#define rep2(i, j, x, y) rep(i, x) rep(j, y)

template <typename T>
inline bool chmin(T &a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template <typename T>
inline bool chmax(T &a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

template <typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
    os << p.first << " " << p.second;
    return os;
}
template <typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p) {
    is >> p.first >> p.second;
    return is;
}
template <typename T>
ostream &operator<<(ostream &os, const vector<T> &v) {
    for (int i = 0; i < (int)v.size(); i++) {
        os << v[i] << (i + 1 != (int)v.size() ? " " : "");
    }
    return os;
}
template <typename T>
ostream &operator<<(ostream &os, const set<T> &s) {
    os << vec<T>(s.begin(), s.end());
    return os;
}
template <typename T>
istream &operator>>(istream &is, vector<T> &v) {
    for (T &in : v) is >> in;
    return is;
}
void print() { cout << '\n'; }
template <typename T>
void print(const T &t) {
    cout << t << '\n';
}
template <typename Head, typename... Tail>
void print(const Head &head, const Tail &...tail) {
    cout << head << ' ';
    print(tail...);
}
void print_accurate(dbl x) {
    cout << scientific << setprecision(15) << x << '\n';
}

void repr_(const ll &x) { cerr << x; }
void repr_(const int &x) { cerr << x; }
void repr_(const dbl &x) { cerr << x; }
void repr_(const str &x) { cerr << x; }
void repr_(const char &x) { cerr << x; }
void repr_(const char *x) { cerr << x; }
template <typename T1, typename T2>
void repr_(const pair<T1, T2> &p);
template <typename T1, typename T2>
void repr_(const map<T1, T2> &m);
template <typename T>
void repr_(const vec<T> &v);
template <typename T>
void repr_(const set<T> &s);
template <typename T1, typename T2>
void repr_(const pair<T1, T2> &p) {
    cerr << '(';
    repr_(p.first);
    cerr << ", ";
    repr_(p.second);
    cerr << ')';
}
template <typename T>
void repr_(const vec<T> &v) {
    cerr << '[';
    for (int i = 0; i < (int)v.size(); i++) {
        repr_(v[i]);
        if (i + 1 != (int)v.size()) cerr << ", ";
    }
    cerr << ']';
}
template <typename T>
void repr_(const set<T> &s) {
    cerr << '{';
    vec<T> v = vec<T>(all(s));
    for (int i = 0; i < (int)v.size(); i++) {
        repr_(v[i]);
        if (i + 1 != (int)v.size()) cerr << ", ";
    }
    cerr << '}';
}
template <typename T1, typename T2>
void repr_(const map<T1, T2> &m) {
    cerr << '{';
    vp<T1, T2> v = vp<T1, T2>(all(m));
    for (int i = 0; i < (int)v.size(); i++) {
        repr_(v[i].first);
        cerr << ": ";
        repr_(v[i].second);
        if (i + 1 != (int)v.size()) cerr << ", ";
    }
    cerr << '}';
}
template <typename Head, typename... Tail>
void repr_(const Head &head, const Tail &...tail) {
    repr_(head);
    repr_(' ');
    repr_(tail...);
}
template <typename T>
void repr(const T &t) {
    repr_(t);
    cerr << '\n';
}
template <typename Head, typename... Tail>
void repr(const Head &head, const Tail &...tail) {
    repr_(head);
    repr_(' ');
    repr(tail...);
}

void solve() {
    LL(N);
    VL(A, N);
    unordered_map<ll, vl> d;
    rep(i, N) {
        if (d.find(A[i]) != d.end()) {
            d[A[i]].push_back(i);
        } else {
            d[A[i]] = vl(1, i);
        }
    }
    ll ans = 0;
    reps(k, 1, 2000) {
        for (auto &i : d) {
            vl a = {i.first, 0, 0, 0};
            a[1] = a[0] + k + 10;
            a[2] = a[1] - k;
            a[3] = a[2] + k + 1;
            bool f = false;
            rep(j, 4) {
                if (d.find(a[j]) == d.end()) f = true;
            }
            if (f) continue;
            vpl tmp;
            rep(x, 4) {
                for (auto &j : d[a[x]]) {
                    tmp.push_back({j, x});
                }
            }
            sort(all(tmp));
            // print("tmp", tmp);
            // print("a", a);
            vl dp = {1, 0, 0, 0, 0};
            for (auto &j : tmp) {
                dp[j.second + 1] += dp[j.second];
            }
            // print("dp", dp);
            ans += dp[4];
        }
    }
    print(ans);
}

int main() {
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    solve();
    return 0;
}