#include <iostream>
#include <fstream>
#include <algorithm>

using namespace std;

int main()
{
ifstream fin ("ntri.in");
ofstream fout ("ntri.out");
int n,i,a[800],y,j,nr=0;
fin >>n;
for (i=1;i<=n;++i){
fin>>a[i];
}
sort(a,a+n);
for (i=1;i<=n-2;i++){
        for (j=i+1;j<=n-1;j++){
            for (y=j+1;y<=n;y++){
                if (a[i]+a[j]>=a[y])
                    nr++;
                else
                    break;
            }
        }
    }
    fout << nr;

    return 0;
}