#include <fstream>
#include <algorithm>
using namespace std;

int main()
{
    ifstream in("nrtri.in");
    ofstream out("nrtri.out");
    long n, v[1000], s=0;
    in>>n;
    for(long i=0; i<n; ++i) in>>v[i];
    sort(v, v+n);
    for(long i=0; i<n-2; ++i)
    {
        for(long j=i+1; j<n-1; ++j)
            s+=upper_bound(v+j, v+n, v[i]+v[j])-1-v-j;
    }
    out<<s<<endl;
    in.close(); out.close();
    return 0;
}