#include <iostream>
#include <fstream>

std::ifstream f("nrtri.in");
std::ofstream g("nrtri.out");

const int NMAX = 800;
int n,v[NMAX + 5];

int main(){
    
    f >> n;
    
    for(int i = 0;i < n;i++)
        f >> v[i];
    
    long long sol{};
    for(int i = 0;i < n;i++)
        for(int j = i + 1;j < n;j++)
            for(int k = j + 1;k < n;k++)
                if(v[k] <= v[j] + v[i])sol++;
    
    g << sol;
    
    f.close();
    g.close();
    return 0;
}