#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");
int a[805];
int cautbin(int x, int lo, int hi,int i, int j)
{
    int ans=0;
    while(lo<=hi)
    {
        int mid=(lo+hi)/2;
        if(x>=a[mid] && mid!=j &&mid!=i){ans++;}
        if(x<a[mid]) hi=mid-1;
        else lo=mid+1;
    }
    return ans;
}
int main()
{
    int n,sol=0;
    fin>>n;
    for(int i=1;i<=n;i++) fin>>a[i];
    sort(a+1,a+n+1);
    for(int i=1;i<n;i++)
        for(int j=i+1;j<=n;j++)
        {
            sol+=cautbin(a[i]+a[j],j+1,n,i,j);
        }
    fout<<sol<<"\n";
}