#include<cstdio>
#include<algorithm>
using namespace std;
int n,i,j,v[5000];
void read()
{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    scanf("%d",&n);
    for(i=1;i<=n;i++)
        scanf("%d",&v[i]);
    v[n+1]=100000;
}

bool comp(int a, int b)
{
    return a<b;
}

bool triunghi(int a, int b, int c)
{
    if(a+b>=c)
        return true;
    return false;
}

int cautbin(int st, int dr)
{
    int m;
    m=(st+dr)/2;
    if(st==dr)
        return m;
    if(triunghi(v[i],v[j],v[m]) && !triunghi(v[i],v[j],v[m+1]))
       return m;
    if(v[m]>=v[i]+v[j])
        return cautbin(st,m-1);
    else
        return cautbin(m+1,dr);
}

void rez()
{

    sort(v+1,v+n+1,comp);
    /*int u=0;
    for(int i=1;i<=n;i++)
        if(a[i]!=a[i+1])
            v[++u]=a[i];
    n=u;
   for(int i=1;i<=n;i++)
        printf("%d ",v[i]);
    printf("\n"); */

    int num=0,val;
    for(i=1;i<=n;i++)
        for(j=i+1;j<=n;j++)
        {
            val=cautbin(j,n);
            num=num+val-j;
            //printf("%d %d %d %d \n",v[i],v[j],v[val],val);
        }
    printf("%d\n",num);
}

int main()
{
    read();
    rez();
    return 0;
}