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

ifstream f("nrtri.in");
ofstream g("nrtri.out");
int v[805];
int main()
{
    int n,s=0;;
    f>>n;
    for(int i=1;i<=n;++i)
        f>>v[i];
    sort(v+1,v+n+1);
    for(int i=1;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])
                    ++s;
                else
                    k=n+1;
    g<<s;
    return 0;
}