#include <cstdio>
#include <algorithm>
using namespace std;
int v[801];
int main()
{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);

    int n,i,j,k,a,b,c,nr=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(k=j+1;k<=n;k++)
            {
                c=v[k];
                if(c>a+b)
                    break;
                nr++;
            }
        }
    }
    printf("%d",nr);
    return 0;
}