C language, line skipping the second scanf and go straight to invaliid input

Question

I tried test the code seperately. If I only leave one scanf on in the program , it would work and go through the switch statement. However, once I put two scanf function in the program the program will only read the first one and auto skipped to default. Can someone help me fix this please?

#include <stdio.h>
//#include <conio.h>
#include <math.h>
#include <curses.h>
int main() {

double baseLength, height;
char letter;


    printf("Enter the base length and the height of the square pyramid in centermeter please.\n");
    scanf("%lf%lf",&baseLength,&height);
    printf("%lf%lf\n",baseLength,height);
    printf("P. Calculate and display the perimeter of the base of the square pyramid\n");
    printf("A. Calculate and display the surface area of the square pyramid\n");
    printf("V. Calculate and display the volume of the square pyramid\n");
    printf("Please input P / A / V to choose the desire calculation\n");
    scanf("%c",&letter);
    
    switch(letter)
    {
        case 'P':
        case 'p':
            printf("P");
            break;
        
        case 'A':
        case 'a':
            printf("A");
            break;
        
        case 'V':
        case 'v':
            printf("V");
            break;
        
        default:
            printf("Invalid Input");
             getch();
             return 0;
        
    }

getch();
return 0;

}