#include <cstdio>
#include <algorithm>
using namespace std;
int i,n,j,k,v[810],sol;
int main()
{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    scanf("%d",&n);
    for(i=1;i<=n;i++)
        scanf("%d",&v[i]);
    sort(v+1,v+n+1);
    for(i=1;i<=n;i++)
    {
        for(j=i+1;j<=n;j++)
        {
            k = lower_bound(v+j+1,v+n+1,v[i]+v[j]+1)-v;
            sol += k-j-1;
        }
    }
    printf("%d\n",sol);
    return 0;
}