#include <fstream>
#include <string>
#include <algorithm>
using namespace std;

ifstream cin("baseball.in");
ofstream cout("baseball.out");
int n;
int a[1001];
int s=0;
int main(){
    cin>>n;
    for(int i=0;i<n;i++){
        cin>>a[i];
    }
    sort(a,a+n);
    for(int i=0;i<n;i++){
        for(int j=i+1;j<n;j++){
            for(int k=j+1;k<n;k++){
                if(a[j]-a[i]<=a[k]-a[j] && 2*(a[j]-a[i])>=a[k]-a[j])s++;
            }
        }
    }
    cout<<s<<endl;
}