#include <fstream>
#include <algorithm>
using namespace std;
ifstream in("nrtri.in");
ofstream out("nrtri.out");
int v[801];
int main()
{
    int n,i,j,s,pp=1,cnt=0,k;
    in>>n;
    for(i=1; i<=n; i++)
        in>>v[i];
    sort(v+1,v+n+1);
    for(i=1; i<=n-2; i++)
    {
        k=i+2;
        for(j=i+1; j<=n-1; j++)
        {
            while(k<=n&&v[k]<=v[i]+v[j])
                k++;
            if(k-j-1>0)
                cnt+=k-j-1;
        }
    }
    out<<cnt;
    return 0;
}