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

ifstream in("nrtri.in");
ofstream out("nrtri.out");



int v[1001], ok = 0;


int main()
{
    int n,ok=0,cnt=0;
    in >> n;
    for(int i=1;  i<=n;i++)
        in>>v[i];
    sort( v+1,v+n+1);
    for( int j=1;j<=n;j++ )
    {

        for( int i=1;i<j;i++)
        {
            while( cnt<n&&v[cnt+1]<=v[j]+v[i])
                cnt++;
            ok += max(0,cnt-j);
        }
    }
    out <<ok ;
    return 0;
}