#include <fstream>
#include <cstdlib>

using namespace std;

int compare_ints(const void* a, const void* b)
{
    int arg1 = *reinterpret_cast<const int*>(a);
    int arg2 = *reinterpret_cast<const int*>(b);
    if(arg1 < arg2) return -1;
    if(arg1 > arg2) return 1;
    return 0;
}

int v[1000];

int main()
{int i, n, j, l, k = 0;
    ifstream in("nrtri.in");
    ofstream out("nrtri.out");
    in >> n;
    for (i = 0; i < n; ++i)
        in >> v[i];
    qsort(v, n, sizeof(int), compare_ints);
    for (i = 0; i < n-2; ++i)
        for (j = i+1; j < n-1; ++j)
            for (l = j+1; l < n; ++l)
            {
                if (v[i]+v[j] >= v[l])
                    ++k;
                else
                    break;
            }
    out << k << '\n';

    return 0;
}