#include <iostream>
#include <fstream>

using namespace std;

int main()
{ ifstream f("nrtri.in");
ofstream g("nrtri.out");
unsigned int n;
f>>n;
unsigned int v[800],i,j,aux,k,nr=0;;
for(i=0;i<n;i++)
    f>>v[i];
for(i=0;i<n-1;i++)
    for(j=i+1;j<n;j++)
        if(v[i]>v[j])
            {
                aux=v[i];
                v[i]=v[j];
                v[j]=aux;
            }
j=n-1; i=0;
while(i<n)
{
    for(k=i+1;k<j;k++)
        if((v[k]+v[i]>=v[j])&& (v[k]+v[j]>=v[i]) && (v[i]+v[j]>=v[k]))
            nr++;
i++;
}

cout<<nr;
f.close();
g.close();
    return 0;

}