Problem 563. How to add?

• Imagine you are in 2222 Anno Domini, when everyone must learn how to add,
• and competing for the highly prestigious post of,
• Chief Comptroller of Dda Corporation.
• You are being tested via MATLAB Cody for addition of two positive integers X and Y,
• both are fortunately in decimal system, and only a few dozen digits or less,
• and delivered as ASCII strings.
• Please output the result Z in similar style.
• Please adopt a general strategy, as X and Y may be changed later.
• Please rename the function Z = dda(X,Y).
• Function Template:

function Z = dda(X,Y)
   X='98765432109876543210987654321098765432109876543210987654321'
   Y='98765432109876543210987654321098765432109876543210987654321'
   Z='197530864219753086421975308642197530864219753086421975308642';
end