#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;
int i,n,k,j,m,s,dr,x,ok,y,sol;


int main()
{
    freopen ("nrtri.in","r",stdin);
    freopen ("nrtri.out","w",stdout);
    int v[20000100];
    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++)
    {
        for(j=i+1;j<=n-1;j++)
        {
            for(k=j+1;k<=n;k++)
            {
                if(v[i]+v[j]>=v[k])
                sol++;
                else break;
            }
        }
    }
    printf("%d\n",sol);
}