#include <fstream>
#include <vector>
#include <algorithm>
using namespace std;
ifstream cin("nrtri.in");
ofstream cout("nrtri.out");
vector<int>v;
int main(){

ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int n;
cin>>n;
v.resize(n+1);
for(int i=1;i<=n;i++){
    cin>>v[i];
}
sort(v.begin()+1,v.end());

int nr1,nr2,nr3;
int cont=0;
for(int i=1;i<=n-2;i++){
    nr1=i;
    for(int j=i+1;j<=n-1;j++){
        nr2=j;
        nr3=j+1;
        while(nr3<n && v[nr3]>v[nr1]+v[nr2]){
            nr3+=1;
        }
        cont+=nr3-nr2-(v[nr3]>v[nr1]+v[nr2]);

    }
}
cout<<cont;
}