#include<cstdio>
#include<algorithm>
using namespace std;
int i,j,k,n,v[801],nr,x;
int main ()
{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    scanf("%d",&n);
    for(i=1;i<=n;i++)
        scanf("%d",&v[i]);
    sort(v+1,v+n+1);
    for(i=1;i<n-1;i++)
        for(j=i+1;j<n;j++)
        {
            x=v[i]+v[j];
            k=j+1;
            while(v[k]<=x && k<=n)
                k++;
            nr=nr+k-j-1;
        }
    printf("%d",nr);
    return 0;
}