#include<cstdio>
#include<cmath>
#include<algorithm>
using namespace std;
int v[801],i,j,k,n,nr;
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-2;i++)
    for(j=i+1;j<=n-1;j++)
    for(k=j+1;k<=n;k++)
    if(v[i]+v[j]>=v[k])
    nr++;
    else break;
    fprintf(fout,"%d",nr);



    return 0;
}