#include <iostream>
#include <vector>
#include <algorithm>
#include <cstdio>

using namespace std;

int n,aux,nr;



int main()
{
    freopen("nrtri.in","r", stdin);
    freopen("nrtri.out", "w", stdout);

    vector<int> v;

    cin>>n;

    for(int i=1; i<=n; i++)
    {
        cin>>aux;
        v.push_back(aux);

    }
sort(v.begin(),v.end());

for(int i=0; i<n-2; i++)
for(int j=i+1; j<n-1; j++){
    for(int k=j+1; k<n; k++)if((v[i]+v[j])>= v[k])nr++; else {break;}
}
cout<<nr;
    return 0;
}