#pragma GCC optimize("O3")
#pragma GCC optimize("fast-math")
#pragma GCC optimize("unroll-loops")
#include<bits/stdc++.h>
#include<complex>
using namespace std;
int n, sol, st, dr, mid, v[805];
typedef complex<double> point;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");
int32_t main(int argc, char * argv[])
{
    fin >> n;
    for(int i = 1; i <= n; ++i)
        fin >> v[i];
    sort(v + 1, v + n + 1);
    for(int i = 1; i < n - 1; ++i)
        for(int j = i + 1; j < n; ++j)
        {
            st = j + 1, dr = n, mid = 0;
            int vl = 0;
            while(st <= dr)
            {
                mid = (st + dr) / 2;
                if(v[mid] <= v[i] + v[j] && mid <= n)
                {
                    vl = mid;
                    st = mid + 1;
                }
                else
                    dr = mid - 1;
            }
            sol += dr - j;
        }
    fout << sol;
    return 0;
}