how can i write code on this?

if true
f (a, b) = {      0,      if a mod b = 0
           {    b − (a mod b), otherwise
end

Answer 1

[Birdman]

a=input('Enter a\n');
b=input('Enter b\n');
if ~mod(a,b)
   y=0
else
   y=b-mod(a,b)
end