#include<iostream>
#include<fstream>
#include<algorithm>

using namespace std;

ifstream f("nrtri.in");
ofstream g("nrtri.out");

int t[800],i,j,m,n,s,k,ij;

int caut(int i,int j)
        {
        m=(i+j)/2;
        if(i<=j){
        if(t[m]<=k&&t[m+1]>k||t[m]<=k&&m+1>n)return m;
        else
        if(t[m]<=k)return caut(m+1,j);
        else return caut(i,m);
        }
        else return 0;
        }
int main()
{
f>>n;
for(i=1;i<=n;i++)f>>t[i];
sort(t+1,t+n+1);

s=0;
for(i=1;i<n-1;i++)
for(j=i+1;j<n;j++)
        {
        k=t[i]+t[j];
        ij=caut(j,n);
        if(ij!=0)s+=ij-j;
        }
g<<s;
g.close();
return 0;
}