Dear Statalist, hope everyone is in good health

I want to sum x and y variable in STATA by following command
Code:
gen sumxy = sum(x+y)
i find missing observations in sumxy variable that are accounted from variable x and y

for instance, i try to explain my problem in following picture

i want that sumxy doesn't account missing values of variable x and y during summing (like in the excel sum column E in the below picture).
Array