#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;  
}