#include <cstdio>
using namespace std;
int a[805],i,n,nr,j,k;
int main()
{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    scanf("%d %d\n",&n);
    for (i=1;i<=n;i++)
    {
        scanf("%d\n",&a[i]);
    }
    for (i=1;i<=n-2;i++)
        for (j=i+1;j<=n-1;j++)
            for (k=j+1;k<=n;k++)
            {
                if (a[i]+a[j]>=a[k])
                {
                    nr++;
                }
                else break;
            }
    printf("%d\n",nr);
    return 0;
}