#include<cstdio>
#include<algorithm>
using namespace std;
int n,i,j,p,q,nr,st,dr,m,v[805],sol,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++)
    {
        st=j; dr=n; x=j;
        x=upper_bound(v+1,v+n+1,v[i]+v[j])-v-1;
        sol=sol+x-j;
    }
    printf("%d",sol);
    return 0;
}