#include<cstdio>

using namespace std;

int  a[802],n,i,j,k,nr;

int main()
{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    scanf("%d",&n);
    nr=0;
    for (i=1;i<=n;i++)
    {
        scanf("%d",&a[i]);
    }
    for (i=1;i<=n;i++)
    {
        for (j=i+1;j<=n;j++)
        {
            for (k=j+1;k<=n;k++)
            {
                if ((a[i]+a[j]-a[k]>=0)&&(a[i]+a[k]-a[j]>=0)&&(a[j]+a[k]-a[i]>=0))
                {
                    nr++;
                }
            }
        }
    }
    printf("%d\n",nr);
    return 0;
}