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

ifstream in ("nrtri.in");
ofstream out("nrtri.out");
const int N=802;
int n,tri,v[N];

int cautb(int x)
{
    int rez=0;
    for(int pas=1<<10;pas!=0;pas>>=1)
        if(rez+pas<=n && v[rez+pas]<=x)
            rez+=pas;
    return rez;
}
int main()
{
    in>>n;
    for(int i=1;i<=n;i++)
        in>>v[i];
    sort(v+1,v+n+1);
    for(int i=1;i<n;i++)
        for(int j=i+1;j<=n;j++)
        {
            int temp = cautb(v[i]+v[j]);
            if(temp-j > 0) tri+=temp-j;
        }
    out<<tri;
    return 0;
}