Main.c:10:1: error: unknown type name ‘bool’
   10 | bool isHappy(int n) {
      | ^~~~
Main.c: In function ‘isHappy’:
Main.c:12:16: error: ‘false’ undeclared (first use in this function)
   12 |         return false;
      |                ^~~~~
Main.c:12:16: note: each undeclared identifier is reported only once for each function it appears in
Main.c:18:12: error: ‘true’ undeclared (first use in this function)
   18 |     return true;
      |            ^~~~
Main.c:19:1: warning: control reaches end of non-void function [-Wreturn-type]
   19 | }
      | ^