#include <bits/stdc++.h>

using namespace std;
ifstream fin ("nrtri.in");
ofstream fout ("nrtri.out");
int v[805],i,j,p,cnt,n;
int main()
{
    fin>>n;
    for (i=1;i<=n;i++) fin>>v[i];
    sort (v+1,v+n+1);
    for (i=1;i<=n;i++)
        for (j=i+1;j<=n;j++)
            for (p=j+1;p<=n;p++)
                if(v[i]+v[j]>=v[p]) cnt++;
    fout<<cnt;
    return 0;
}