#include<bits/stdc++.h>
#include<atcoder/fenwicktree>
using namespace std;
#define int long long
int comb(int a){return (a*(a-1))/2;}
signed main(){
    int n;cin>>n;
    map<int,int>edge;
    vector<int>a(n);
    for(int i=0;i<n;i++)cin>>a[i];
    for(int i:a)edge[i]++;
    sort(a.begin(),a.end());
    int ans=0;
    for(auto[i,j]:edge){
        int rt=lower_bound(a.begin(),a.end(),2*i)-a.begin();
        ans+=comb(j)*(rt-j);
    }
    cout<<ans<<endl;
}