#include<stdio.h>
#include<algorithm>
using namespace std;
int v[801];
int main()
{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    int n,i,j,h,aux,a,b,c,mod=0;
    scanf("%d",&n);
    for(i=1;i<=n;i++)
        scanf("%d",&v[i]);
    sort(v+1,v+n+1);
    for(i=1;i<=n-2;i++)
    {
        a=v[i];
        for(j=i+1;j<=n-1;j++)
        {
            b=v[j];
            for(h=j+1;h<=n;h++)
            {
                c=v[h];
                 
                if(a<=b+c&&b<=a+c&&c<=a+b)
                    mod++;
                else
                    if(c>a+b)
                        break;
            }
        }
    }
    printf("%d\n",mod);
    return 0;
}