#include <cstdio>
#include <algorithm>
#define MAX 810
using namespace std;
int v[MAX],sol;
int main()
{
    int n,k,nmare;
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    scanf("%d",&n);
    for(int i=1;i<=n;++i)scanf("%d",v+i);
    sort(v+1,v+n+1);
    for (nmare=1;nmare<=n;nmare<<=1);
    for (int i=1;i<=n-2;++i)
        for (int j=i+1;j<=n-1;++j){
            int k=1;
            for (int step=nmare;step>0;step>>=1)
                if (k+step<=n and v[i]+v[j]>=v[k+step])
                    k+=step;
            sol+=k-j;
        }
    printf("%d\n",sol);
    return 0;
}