#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
int main() {
char x = 99;
char fA = 99;
if ( islower(fA) ){
printf("%s","valid lowercase letter\n");
}
else
{
printf("%s","invalid lowercase ltr\n");
}
char fa = tolower(fA);
char y = tolower(x);
printf("%c %c\n", x,y);
printf("%c %c\n", fA,fa);
return 0;
}