#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
ifstream fi("nrtri.in");
ofstream fo("nrtri.out");

int v[801];

int main()
{
    int i, n, j, rez, k;
    fi>>n;
    for(i=1;i<=n;i++)
        fi>>v[i];
    sort(v,v+n);
    rez=0;
    for(i=1;i<n-1;i++){
        k=i+2;
        for(j=i+1;j<n;j++){
            while(k<=n && v[k]<=v[i]+v[j])
                k++;
            if(k>j)
                rez+=k-j-1;
        }
    }
    fo<<rez;
    return 0;
}