C - Why am I getting two characters excpet one as output?

So I create this small program to represent my problem. Run program enter 'a' press ENTER.

C Code:

#include <stdio.h>
#include <stdlib.h>

int main(void)
{
    char o;
    while(1)
    {
        printf("> ");
        scanf("%c",&o);
        switch(o)
        {
        case 'a' :
            printf("%c\n",o);
            break;
        case 'q' :
            return 0;
        }
    }
}

Output is:

> a
a
> > *(waiting for imput)*

What I expected it to be:

> a
a
> *(waiting for imput)*

Please give me some advice how to get my problem solved. Thank you.