#include <iostream>
#include <algorithm>
#include <fstream>
using namespace std;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");
int x[1000],N,i,j,sol,k;
int main()
{
    fin>>N;
    for(i=1;i<=N;i++)
        fin>>x[i];
    sort(x+1,x+1+N);
    for(i=1;i<=N;i++)
        for(j=i+1;j<=N-1;j++)
        {
            k=j+1;
            while(x[i]+x[j]>=x[k] && k<=N)
            k++;
            sol+=k-j-1;
        }
        fout<<sol;
    return 0;
}