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


using namespace std;

int n,a[10000],nr;

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(int i=1;i<=n-2;i++)
      for(int j=i+1;j<n;j++)
        {int v=a[i]+a[j];
         int st=j+1,dr=n,mij=st+(dr-st)/2;
         while(st<=dr)
           {
            if((a[mij]<=v&&a[mij+1]>v)||(a[mij]<=v&&mij==n))
               break;
              else
                if(a[mij]<v&&a[mij+1]<=v){
                  st=mij+1;
                  mij=(st+dr)/2;
                 }
               else
                {dr=mij-1;
                mij=(st+dr)/2;
                }
           }
        nr=nr+mij-j;

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

int main()
{

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

return 0;
}