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

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

int n,i,j,k,a[801],m=0;



int main()
{
    fin>>n;
    for(i=1;i<=n;++i)
        fin>>a[i];
    sort(a+1,a+n+1);
    for(i=1;i<=n;++i)
    for(j=i+1;j<=n;++j)
    {
        k=j+1;
        while(a[i]+a[j]>=a[k] && k<=n)++k;
        m+=k-j-1;
    }
    fout<<m;
    return 0;
}