#include<fstream>     
using namespace std;     
int main()     
{     
    ifstream in("nrtri.in");     
    ofstream out("nrtri.out");     
    int n,x,j,k,l,v[801],w,i;     
    in>>n;     
    for(i=1;i<=n;i++)     
    {     
        in>>x;     
        v[i]=x;     
    }     
    w=0;     
    for(j=1;j<=n;j++)     
        for(k=j+1;k<=n;k++)     
            for(l=k+1;l<=n;l++)     
                if ((v[j]+v[k]>=v[l])&&(v[j]+v[l]>=v[k])&&(v[l]+v[k]>=v[j])) w++;     
    out<<w;     
    in.close();     
    out.close();     
    return 0;     
}