#include <iostream>
#include <stdio.h>
#include <algorithm>
#define MAX_N 801
using namespace std;
int v[MAX_N], n;
void citire_si_sortare()
{
    freopen("nrtri.in","r",stdin);
    scanf("%d",&n);
    int i;
    for(i=1; i<=n; i++) scanf("%d",&v[i]);
    sort(v+1,v+n+1);
    //for(i=1; i<=n; i++) printf("%d ", v[i]);
}
int caut_binar(int left, int right, int value,int answer)//caut binar pozitia maxima pe care o poate avea latura 3 in vectorul v
{
    if(left<=right)
    {
        int k=(left+right)/2;
        if(v[k]<=value)
        {
            //cout<<v[k]<<endl;
            answer=max(answer,k);
            caut_binar(k+1,right,value,answer);
        }
        else caut_binar(left,k-1,value,answer);
    }
    else return answer;
}
int solve()
{
    int i,j,aux,solutie=0;
    for(i=1; i<=n-2; i++)
    for(j=i+1; j<=n-1; j++)
    {
        aux=caut_binar(j+1,n,v[i]+v[j],j);
        //cout<<i<<' '<<j<<' '<<aux<<endl;
        solutie+=(aux-j);
    }
    return solutie;
}
int main()
{
    freopen("nrtri.out","w",stdout);
    citire_si_sortare();
    printf("%d",solve());
    return 0;
}