/in/foo.cc: In function 'int main()':
/in/foo.cc:8:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    8 |  scanf("%s",str);
      |  ~~~~~^~~~~~~~~~
/in/foo.cc:12:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   12 |  scanf("%s",str);
      |  ~~~~~^~~~~~~~~~
/in/foo.cc:22:2: warning: 'j' may be used uninitialized in this function [-Wmaybe-uninitialized]
   22 |  if(j)len++;//最后一位是否进位
      |  ^~