#include <cstdio>
#include <algorithm>

using namespace std;
const int NMAX = 805;
int v[NMAX];
int n;

int caut_bin(int s,int d,int x)
{
    int st,dr,med,ans=0;
    st = s;
    dr = d;
    while(st<=dr)
    {
        med = (st+dr)/2;
        if(v[med]<=x)
        {
            ans=med;
            st=med+1;
        }
        else
            dr=med-1;
    }
    return ans;
}

int main()
{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    int m;
    long long int nr = 0;
    scanf("%d",&n);
    for(int i = 1 ; i <= n ; i++)
        scanf("%d",&v[i]);
    sort(v+1,v+n+1);
    for(int i = 1 ; i < n ; i++)
    {
        for(int j = i+1 ; j <= n ; j++)
        {
            int answer = caut_bin(j+1,n,v[i]+v[j]);
            if(answer!=0)
            nr += (answer-j);
        }
    }
    printf("%d",nr);
    return 0;
}