#include <fstream>
#include <algorithm>
using namespace std;
ifstream in ("nrtri.in");
ofstream out ("nrtri.out");
const int N=802;
int v[N],n;

int cautbin(int a,int b)
{
    int s=a+b,pas=1<<9,r=0;
    while (pas)
    {
        if (r+pas<=n && v[r+pas]<=s)
            r+=pas;
        pas/=2;
    }
    return r;
}
int main()
{
    int i,j,cnt=0;
    in>>n;
    for (i=1;i<=n;i++)
        in>>v[i];
    sort(v+1,v+n+1);
    for (i=1;i<=n;i++)
        for (j=i+1;j<=n;j++)
            cnt+=cautbin(v[i],v[j])-j;
    out<<cnt;
    return 0;
}