#include<cstdio>
#include<algorithm>

using namespace std;

int n,v[801];

int main()
{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);

    scanf("%d",&n);

    for(int i=1;i<=n;i++)
    {
        scanf("%d",&v[i]);
    }

    sort(v+1,v+n+1);

    int p=3;
    int res=0;
    for(int i=1;i<n;i++)
    {
        p=i+1;
        for(int j=i+1;j<=n;j++)
        {
            while(v[i]+v[j]>=v[p]&&p<=n)
            {
                p++;
            }
            p--;
            res+=p-j;
        }
    }

    printf("%d",res);
}