#include <cstdio>
#include <algorithm>
using namespace std;
int v[801];
int main()
{
    FILE *f, *g;
    f=fopen("nrtri.in","r");
    g=fopen("nrtri.out","w");
    int n,i,j,k,s=0;
    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-2;i++)
        for (j=i+1;j<=n-1;j++)
            for (k=j+1;k<=n;k++)
            {
                if (v[i]+v[j]>=v[k])
                    s++;
                else break;
            }
    fprintf(g,"%d",s);
    return 0;
}