#include <cstdio>
#include <algorithm>

FILE *f=fopen("nrtri.in","r");
FILE *g=fopen("nrtri.out","w");

using namespace std;

int n,i,v[801],j,nr,poz;

int main()
{
    fscanf(f,"%d",&n);
    for (i=1;i<=n;i++)
        fscanf(f,"%d",&v[i]);

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

    for (i=1;i<=n-1;i++)
        for (j=i+1;j<=n;j++)
        {
            poz=upper_bound(v+j+1,v+n+1,v[i]+v[j])-(v+1);
            //fprintf(g,"%d %d %d %d\n",i,j,poz,nr);
            nr=nr+poz-j;

        }

        fprintf(g,"%d",nr);

    fclose(f);
    fclose(g);
}