When you tried to submit codes containing something (I cannot show it here, because it will be blocked, but it is the string that is the output of the program i'll give in the end of this blog), it redirects you to a Cloudflare page which says that you have been blocked.

MikeMirzayanov Please check this.

The code that will output the banned substring:

main() {
printf("c");
printf("=");
printf("c");
printf("h");
printf("a");
printf("r");
printf("(");
printf("\'");
printf("a");
printf("\'");
printf(")");
}