#include <cstdio>
#include <vector>
#include <algorithm>

using namespace std;

int main()
{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    int n , i , nr;
    vector<int>v;
    scanf("%d",&n);
    for(i=0;i<n;i++)
    {
        scanf("%d",&nr);
        v.push_back(nr);
    }
    int s=0;
    sort(v.begin(),v.end());
    vector<int>::iterator it,it1,it2;
    for(it=v.begin();it!=v.end();it++)
        for(it1=it+1;it1!=v.end();it1++)
    {
        int sum=(*it)+(*it1);
        it2=upper_bound(v.begin(),v.end(),sum);
        int x=it2-it1-1;
        s+=x;
    }
    printf("%d",s);
    return 0;
}