#include <cstdio>
#include <algorithm>
#include <vector>
FILE *f=fopen("nrtri.in","r");
FILE *g=fopen("nrtri.out","w");
using namespace std;
vector <int>v;
int nrsol,n;
void solve()
{
    int i,j,k;
    for(i=0;i<n-2;i++)
        for(j=i+1;j<n-1;j++)
            for(k=j+1;k<n;k++)
                if(v[i]+v[j]>=v[k])
                    nrsol++;
                else
                    break ;
    fprintf(g,"%d\n",nrsol);
}
int main()
{
    int x;
    fscanf(f,"%d",&n);
    for(int i=1;i<=n;i++)
        {
            fscanf(f,"%d",&x);
            v.push_back(x);
        }
    sort(v.begin(),v.end());
    solve();
    return 0;
}