I have a problem with a code which works on my laptop but not on sololearn

Question

#include <iostream>
using namespace std;
#include <stdio.h>
#include <stdlib.h>
#include<ctype.h>

int main()
{
char c;
printf("ENTER TEXT !\n");
while(c=getchar())
if(isupper(c))
putchar(tolower(c));
else
putchar(toupper(c));
return 0;
}

Answer 1

This has been answered.

https://www.sololearn.com/discuss/844871/?ref=app