#include<iostream>
using namespace std;
#include<stdio.h>
FILE *f,*g;
int a[801],i,j,n,m,q;
int main()
{
    f=fopen("nrtri.in","r");
    g=fopen("nrtri.out","w");
    fscanf(f,"%d",&n);
    for(i=1;i<=n;i++)
    {
        fscanf(f,"%d",&a[i]);
    }
    for(i=1;i<=n-3;i++)
        for(j=i+1;j<n;j++)
          for(q=j+1;q<=n;q++)
          if(a[i]+a[j]>=a[q])
          {m++;
          }
    fprintf(g,"%d",m);
}