#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;

int main()
{
    ifstream fin("nrtri.in");ofstream fout("nrtri.out");
    int n,v[810],i,j,a,k,m=0;
    cin>>n;
    for(i=1;i<=n;i++) cin>>v[i];
    sort(v+1,v+n+1);
    for(i=1;i<n-1;i++) for(j=i+1;j<n;j++)
    {
        k=j,a=n;
        while(a>1)
        {
            a=a/2;
            if(v[k+a]<v[i]+v[j]) k=k+a;
        }
        m=m+k-j; //cout<<m<<"  ";
    }
    cout<<m;
    return 0;
}