foo.cc:63:46: error: empty character constant
   63 |                                         puts('');
      |                                              ^~
foo.cc: In function ‘bool cmp(Node, Node)’:
foo.cc:10:41: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses]
   10 |         return x.num<y.num||x.num==y.num&&x.id<y.id;
      |                             ~~~~~~~~~~~~^~~~~~~~~~~
foo.cc: In function ‘int main()’:
foo.cc:63:46: error: invalid conversion from ‘char’ to ‘const char*’ [-fpermissive]
   63 |                                         puts('');
      |                                              ^~
      |                                              |
      |                                              char
In file included from /nix/gcc-14.2.1.20250322/include/c++/14.2.1.20250322/cstdio:42,
                 from /nix/gcc-14.2.1.20250322/include/c++/14.2.1.20250322/ext/string_conversions.h:45,
                 from /nix/gcc-14.2.1.20250322/include/c++/14.2.1.20250322/bits/basic_string.h:4154,
                 from /nix/gcc-14.2.1.20250322/include/c++/14.2.1.20250322/string:54,
                 from /nix/gcc-14.2.1.20250322/include/c++/14.2.1.20250322/bitset:52,
                 from stdc++.h:52:
/nix/glibc-2.40-66-dev/include/stdio.h:714:30: note:   initializing argument 1 of ‘int puts(const char*)’
  714 | extern int puts (const char *__s);
      |                  ~~~~~~~~~~~~^~~