#include <fstream>
#include <algorithm>
using namespace std;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");
int a[100001],j,s,n,i;
bool comp(int a,int b)
{
    return a<b;
}
int main()
{
    fin>>n;
    for(i=1;i<=n;i++)
        fin>>a[i];
    sort(a+1,a+1+n,comp);
    for(i=1;i<=n-2;i++)
        for(j=i+1;j<=n-1;j++)
            s+=upper_bound(a+j,a+n+1,a[i]+a[j])-a-1-j;
    fout<<s;
    return 0;
}