foo.cc: In function 'int main()':
foo.cc:16:19: error: unable to find numeric literal operator 'operator""\U0000ff1b'
   16 |                 j=0；
      |                   ^~~
foo.cc:16:19: note: use '-fext-numeric-literals' to enable more built-in suffixes
foo.cc:19:15: error: 'b' was not declared in this scope
   19 |         while(b<x-1)
      |               ^

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