#include <fstream>
using namespace std;
ifstream cin("nrtri.in");
ofstream cout("nrtri.out");
int main()
{
    int v[802], n, ans = 0;
    cin >> n;
    for(int i=1;i<=n;i++) cin >> v[i];
    for(int a=1;a<=n-2;a++)
        for(int b=a+1;b<=n-1;b++)
            for(int c=b+1;c<=n;c++)
                if(v[a]+v[b]>=v[c] and v[a]+v[c]>=v[b] and v[b]+v[c]>=v[a])
                    ans++;
    cout << ans;
    return 0;
}