foo.cc: In function ‘int huiwen(int)’:
foo.cc:24:13: warning: statement has no effect [-Wunused-value]
   24 |         for(n;n>=1;n--)
      |             ^
foo.cc: In function ‘int number(int)’:
foo.cc:38:13: warning: variable ‘w’ set but not used [-Wunused-but-set-variable]
   38 |         int w,sum;
      |             ^