Replace
for i=1;length(V)
with
for ii = 1:length(V)
The semicolon -> colon is a typo I suspect, and i has a built in value so it's a bad idea to use it as a variable. Right now, your code runs for i=1, displays length(V) (which is 18) and does nothing else.
The line
numChanges + = 1
will fail when it reaches it. Replace it with
numChanges = numChanges + 1;
which won't fail.
