#include <bits/stdc++.h>
#include <atcoder/all>
#include <boost/multiprecision/cpp_dec_float.hpp>
#include <boost/multiprecision/cpp_int.hpp>
namespace mp = boost::multiprecision;
using Bint = mp::cpp_int;
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];
    sort(a.begin(),a.end());
    ll ans = 0;
    map<int, int> mp;
    rep(i,n) mp[a[i]]++;
    dbg(a);
    for(auto p : mp) {
        if(p.second<2) continue; 
        ll it = lower_bound(a.begin(),a.end(),p.first*2) - a.begin();
        ans += (it-p.second)*p.second*(p.second-1)/2;
    }
    cout << ans << endl;
    return 0;
}