#include<cstdio>
int nr,i,j,ij,n,a[801];
int main()
{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    scanf("%d",&n);
    for(i=1;i<=n;i++)
    {
        scanf("%d",&a[i]);
    }
    for(i=1;i<=n-2;i++)
    {
        for(j=i+1;j<=n-1;j++)
        {
            for(ij=j+1;ij<=n;ij++)
            {
                if(a[i]<=a[j]+a[ij]&&a[j]<=a[i]+a[ij]&&a[ij]<=a[i]+a[j]) nr++;
            }
        }
    }
    printf("%d",nr);
    return 0;
}