#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int main(){
    int n,x;
    vector<int> v;
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    cin>>n;
    for(int i=0;i<n;i++){
        cin>>x;
        v.push_back(x);
    }
    
    sort(v.begin(),v.end());
    long long ans = 0;
    for(vector<int> ::iterator iti = v.begin();iti!=v.end();iti++) {
        for(vector<int>::iterator itj = iti+1;itj!=v.end();itj++) {
            ans+=(int)((upper_bound(itj+1, v.end(), *iti+*itj)-(itj+1)));
        }
    }
    
    cout<<ans;
    return 0;
}