#include <fstream>
#define N 1000
using namespace std;

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

int n,a[N];

void QSort(int st,int dr)
{
    if(st<dr)
    {
        int m=st+(dr-st)/2,aux=a[st];
        a[st]=a[m];
        a[m]=aux;
        int i=st,j=dr,d=0;
        while(i<j)
        {
            if(a[i]>a[j])
            {
                aux=a[i];
                a[i]=a[j];
                a[j]=aux;
                d=1-d;
            }
            i+=d;
            j-=(1-d);
        }
        QSort(st,i-1);
        QSort(i+1,dr);
    }
}

int main()
{
    int i;
    fin>>n;
    for(i=1; i<=n; ++i) fin>>a[i];
    QSort(1,n);

    int j,k,ct=0;
    bool ok;
    for(i=1; i<=n-2; ++i)
        for(j=i+1; j<=n-1; ++j)
        {
            ok=0;
            for(k=j+1; k<=n && ok==0; ++k)
              if(a[k]>=a[i]+a[j]) ok=1;
              else ct++;
        }
    fout<<ct;
    return 0;
}