Help needed!!!How to write STATA code to count the number for the following question?

I have 5 variables (a1,a2,a3,a4,a5), all of which are categorical and coded as 0=no, 1=yes,98=refuse to report, 99=unknown. I need to calculate the number of observations with 1) 1 or more responded with "yes"; 2) more than 3 responded "yes". How to write STATA code for this purpose?

Thanks so much for your help!!!