Setting up something that is limited to a value within an array?

Question

I am currently working on a project and I'm not entirely sure how to do this but I want to have an if statement that has something along the lines of this

if(a != b[]){
    printf("Use another value!");
}

Where b[] is any value within the array. So for example if I have 100 values and what the user inputted was not any of those then it would then print "Use another value!"

I thought I should specify that I am doing this is C

Answer 1

in C# you can go

ArrayVariable.Contains(object)

Answer 2

you can iterate thorugh the loop and check it's value

for(int i=0;i<sizeof(b);i++)
{
   if(a!=b[i]
   {
    printf("Use another value");
    break;
  }
}

i guess its done in this way.I have not really used C in a long time.