#include <stdio.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

int main(int argc, char const *argv[])
{
    int flags = fcntl(STDIN_FILENO, F_GETFL);
    flags ^= O_NONBLOCK;
    fcntl(STDIN_FILENO, F_SETFL, flags);
    return 0;
}