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

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

int a[810],n;

int cautare( int x, int y)
{
    int m,in,sf;

in=y+1;sf=n;
    while( x < y )
    {
        m=(x-y)/2;
        if( a[x]+a[y]> a[m] )
            return 1;
        else
            in = m + 1;
    }
    return 0;
}
int main()
{ int i,j,nr=-1;
    f>>n;
    for (i=1; i<=n; i++)
        f>>a[i];

    sort(a+1,a+n+1);

   for(i=1;i<n;i++)
        for (j=i+1; j<n; j++)
            nr += ( cautare( a[ i ], a[ j ]));
   g<<nr;

    return 0;
}