#include <cstdio>
#include <vector>
#include <algorithm>
using namespace std;
vector <int> v;
int main()
{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    int i,n,cnt=0,x;
    scanf("%d",&n);
    for(i=1;i<=n;i++)
    {
        scanf("%d",&x);
        v.push_back(x);
    }
    sort(v.begin(),v.end());
    vector<int>::iterator it1,it2,it3;
    for(it1=v.begin();it1!=v.end();it1++)
        for(it2=it1+1;it2!=v.end();it2++)
        {
            it3=upper_bound(v.begin(),v.end(),((*it1)+(*it2)));
            cnt+=(it3-it2-1);
        }
    printf("%d",cnt);
    return 0;
}