#include <iostream>
#include <fstream>

using namespace std;
int a[801];
int main()
{ifstream fin("nrtri.in");
ofstream fout("nrtri.out");
int i,j,k,n,nr=0;
fin>>n;
for(i=1;i<=n;i++)
    fin>>a[i];
for(i=1;i<n-1;i++)
    for(j=i+1;j<n;j++)
        for(k=j+1;k<=n;k++)
            if(a[i]+a[j]>=a[k]&&a[i]+a[k]>=a[j]&&a[k]+a[j]>=a[i])
                nr++;
fout<<nr;
    return 0;
}