foo.cc: In function 'int main()':
foo.cc:11:23: error: 'x1' was not declared in this scope; did you mean 'n1'?
   11 |                 while(x1<x)   // 出门 x1==x
      |                       ^~
      |                       n1
foo.cc:11:26: error: 'x' was not declared in this scope
   11 |                 while(x1<x)   // 出门 x1==x
      |                          ^