Input only number C programming

Question

currently i am doing a program to get the input (0 to 50) from the user. If the number is out of the range then the number will not be counted. After that, i will calculate and

Answer 1

You could choose among options:
A. Take input as string and then verify if the string is number. Else, discard it.
B. Trap key downs. If if is alphabet or symbol, discard. If 0-9, use it.