THIS IS LANGUAGE 'C' NOT C++

The Problem is, even though I use two 'scaf' to input two different character, as you can see in the picture, one of the two 'scanf' that scans character gets skipped; as a result, the code executes --> "floating exception (core dumped)"

But for my homework, I have to input two different characters (just one letter (it could be capital and it could be lower case ) and the task is to play around with ASCII Table with the two input characters; and I have no clue why this is giving me such an error. PLEASE HELP ME~!!

printf("size of bite-" scanf("%d", &size b) printf("Input Letter (G T M)" scanf ( " % c" , &prefix); printf("b or B"); scanf ("%d", &unit); size of bite -->3 Input Letter (G T M) --> b or B two separate "scanf