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

#define MAXN 801
using namespace std;

int i,j,k,N,counts,v[MAXN];

int main()
{
    FILE*in=fopen("nrtri.in","r");
    FILE*out=fopen("nrtri.out","w");
    
    fscanf(in,"%d",&N);
    
    for( i = 1; i <= N ; i++)
     fscanf(in,"%d",&v[i]);
    sort(v+1 ,v+N+1);
    
    for( i = 1; i <= N ; i++)
     for( j = i + 1; j <= N ; j++)
      for( k = j + 1; k <= N ; k++)
      {
           if(v[i] + v[j] < v[k]) break;
            else counts++;
      }
      
fprintf(out,"%d\n",counts);

return 0;
}