#include<fstream>
using namespace std;

int main()
{
    long i,n,v[1001],a,b,c,k;
    ifstream fin("ntri.in");
    ofstream fout("ntri.out");
    k=0;
    
    fin >> n;
    
    for(i = 1;i<=n;i++)
        fin >> v[i];
    
    for(a = 1;a<=n-2;a++)
        for(b = a+1;b<=n-1;b++)
            for(c = b+1;c<=n;c++)
            {
                if(v[a]+v[b]>=v[c] && v[b]+v[c]>=v[a] && v[a]+v[c]>=v[b]){
                   k++;
                   }
            }
    
    fout << k;
    
    return 0;}