if user inputs something like "blablabla" scanf will not be able to convert it to int- so the string will be left in the input buffer as is.
if you use continue and do nothing to the input buffer next iteration will try to read the same string and will fail as well
you need to get rid of the "blablabla" string before asking user to enter something else. REad FAQ how to do it
FAQ > How do I... (Level 2) > Flush the input buffer