#include <iostream>
#include <fstream>

using namespace std;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");

int main()
{
    long long i,j,a[801],z,n,s=0;
    fin>>n;
    for(i=1;i<=n;i++)
    fin>>a[i];
    for(i=1;i<=n-2;i++)
        for(j=i+1;j<=n-1;j++)
            for(z=j+1;z<=n;z++)
            if(a[i]>0 && a[j]>0 && a[z]>0 && a[i]+a[j]>a[z])
            s++;
            else break;
        fout<<s;

    fin.close();
    fout.close();
    return 0;
}