#include<stdio.h>
#include <algorithm>


using namespace std;

int n,a[10000],r,l,v;

int binar()
{
    int i, lg;
    for(i=n+1, lg = l; lg; lg >>= 1)
        if(i-lg>0&&a[i-lg]>v)
            i-=lg;


return i;
}

void citire()
{
    scanf("%d",&n);
    for(int i=1;i<=n;i++)
      scanf("%d",&a[i]);
    sort(a+1,a+n+1);
}

void solve()
{
    for(l = 1; l < n + 1; l <<= 1);
    for(int i=1;i<=n-1;i++)
      for(int j=i+1;j<n;j++)
        {v=a[i]+a[j];
         int nr=(binar());
         r+=(nr-1-j);

       }
    printf("%d",r);
}

int main()
{

    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    citire();
    solve();

return 0;
}