#include<cstdio>
#include<cmath>
#include<algorithm>
using namespace std;
int v[801],i,nr,aux,a,b,auxx,s,n,x,j;
FILE *fin=fopen("nrtri.in","r");
FILE *fout=fopen("nrtri.out","w");
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;i++)
    for(j=i+1;j<=n;j++)
    {
        s=v[i]+v[j];
        x=max(v[i]-v[j],v[j]-v[i]);
        for(aux=1;v[aux]<x;aux++);
        for(auxx=aux;v[auxx]<s&&auxx<=n;auxx++);
        if(auxx-aux>0)
        nr+=auxx-aux-2;
    }
    fprintf(fout,"%d",nr-1);



    return 0;
}