#include <stdio.h>

char to_lower(char letter);

int main(void)
{
	char input;

	printf("Please input a letter: \n");

	scanf("%c", &input);

	printf("%c's lowercase is %c\n", input, to_lower(input));

	return 0;
}

char to_lower(char letter)
{
     if (letter >= 'A' && letter <= 'Z') {
        return letter + 32; // Convert to lowercase by adding 32
    } else {
        return '\0'; // Return null character if not uppercase
    }
}