#include <bits/stdc++.h>
#define NMAX 10001
using namespace std;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");
int n,l[NMAX],cnt;
signed main()
{
    fin>>n;
    for(int i=1;i<=n;++i)
    {
        fin>>l[i];
    }
    sort(l+1,l+1+n);

    for(int i=1;i<n;++i)
    {
        for(int j=i+1;j<=n;++j)
        {
            int st=j+1;
            int dr=n;
            int ans=-1;
            while(st<=dr)
            {
                int mid=(st+dr)/2;
                if(l[mid]>l[i]+l[j])
                {
                    dr=mid-1;
                }
                else
                {
                    st=mid+1;
                    ans=mid;
                }
            }
            if(ans!=-1)
                cnt+=ans-j;
        }

    }
    fout<<cnt;

    return 0;
}