#include<cstdio>
int n,i,j,l,nr,a[802];
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(l=j+1;l<=n;l++)
            {
                if(a[i]+a[j]>=a[l]&&a[i]+a[l]>=a[j]&&a[j]+a[l]>=a[i])nr++;
            }
        }
    }
    printf("%d",nr);
    return 0;
}