#include <cstdio>
#include <algorithm>
//#define max(a,b) (a>b)? a:b
using namespace std;

FILE*fin=fopen("nrtri.in","r");
FILE*fout=fopen("nrtri.out","w");

int a,b,i,j,k,n,m,v[1000],rasp;
int main()
{
    fscanf(fin,"%d",&n);
    for (i=1;i<=n;i++)
    fscanf(fin,"%d",&v[i]);
    sort(v+1,v+n+1);
    for (i=1;i<n-1;i++)
    for (j=i+1;j<=n-1;j++)
    {
        a=std::distance(lower_bound(v+i,v+n+1,v[j]-v[i]),upper_bound(v+i,v+n+1,v[i]+v[j])-1);
        rasp+=a;
    }
    fprintf(fout,"%d\n",rasp-n);

    return 0;
}